Zoom lens system

ABSTRACT

A zoom lens system has the first and second lens units. During zooming from a wide-angle end to a telephoto end, the lens units are moved to decrease a distance therebetween. The first lens unit has a positive refractive power. The second lens unit has a negative refractive power. The zoom lens system is provided with at least one surface having a power to diffract light.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/784,177, now U.S. Pat. No. 6,067,196, entitled “Zoom LensSystem”, filed on Jan. 15, 1997 now U.S. Pat. No. 6,067,196, thedisclosure of which is expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system, and particularly toa compact zoom lens system suitable as a talking lens, for example, in alens-shutter camera.

2. Description of the Prior Art

Conventionally, most zoom lens systems for lens-shutter cameras consistof lens units that are each composed of two or more lens elements. Inorder to reduce the size and the cost of such cameras, it is essentialto compose their lens units of as few lens elements as possible.

To achieve the above purpose, U.S. Pat. No. 5,327,290 proposes a zoomlens system consisting of, from the object side, a first lens unithaving a positive refractive power and a second lens unit having anegative refractive power. In this zoom lens system, each lens unit iscomposed of two lens elements. Moreover, Japanese Laid-open PatentApplication No. H3-15881 proposes a zoom lens system consisting of twolens units, one having a positive refractive power and the other havinga negative refractive power. In this zoom lens system, the number oflens elements composing each lens unit is reduced by the use of theaspherical surfaces; specifically, the first lens unit is composed oftwo lens elements, and the second lens unit is composed of as few as onelens element.

However, the zoom lens system proposed in these Japanese Laid-openPatent Applications have a defect in that it cannot satisfactorilycorrect the chromatic aberration over the whole system, because thechromatic aberration within each lens unit cannot be correctedsufficiently at high zooming ratios.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a zoom lens systemthat, despite being compactly constructed of as few lens elements aspossible, is capable of correcting chromatic aberration properly.

To achieve the above object, according to the present invention, in azoom lens system that includes a lens unit having a negative refractivepower disposed at an image-side end and that performs zooming by varyingdistances between a plurality of lens units, said plurality of lensunits include a surface having a power to diffract light.

Specifically, according to one aspect of the present invention, in azoom lens system that comprises, from an object side, a first lens unithaving a positive refractive power and a second lens unit having anegative refractive power and that performs zooming from a wide-angleend to a telephoto end by moving the first and second lens units in sucha way that a distance between the first and second lens units decreases,said zoom lens system includes at least one surface having a power todiffract light.

Alternatively, according to another aspect of the present invention, inthe above described zoom lens system, said first lens unit is composedof at least two lens elements, and said zoom lens system includes atleast one surface having a power to diffract light.

Alternatively, according to still another aspect of the presentinvention, said second lens unit is composed of one lens element.

Alternatively, according to a further aspect of the present invention,said first lens unit is composed of one lens element, said second lensunit is composed of at least two lens elements, and said zoom lenssystem includes at least one surface having a power to diffract light.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a diagram showing the lens construction of the zoom lenssystem of the first embodiment of the present invention;

FIG. 2 is a diagram showing the lens construction of the zoom lenssystem of the second embodiment of the present invention;

FIG. 3 is a diagram showing the lens construction of the zoom lenssystem of the third embodiment of the present invention;

FIG. 4 is a diagram showing the lens construction of the zoom lenssystem of the fourth embodiment of the present invention;

FIG. 5 is a diagram showing the lens construction of the zoom lenssystem of the fifth embodiment of the present invention;

FIG. 6 is a diagram showing the lens construction of the zoom lenssystem of the sixth embodiment of the present invention;

FIG. 7 is a diagram showing the lens construction of the zoom lenssystem of the seventh embodiment of the present invention;

FIGS. 8A, 8B, and 8C are diagrams showing the aberration at thewide-angle end in the first embodiment;

FIGS. 9A, 9B, and 9C are diagrams showing the aberration at the middlefocal length in the first embodiment;

FIGS. 10A, 10B, and 10C are diagrams showing the aberration at thetelephoto end in the first embodiment;

FIGS. 11A, 11B, and 11C are diagrams showing the aberration at thewide-angle end in the second embodiment;

FIGS. 12A, 12B, and 12C are diagrams showing the aberration at themiddle focal length in the second embodiment;

FIGS. 13A, 13B, and 13C are diagrams showing the aberration at thetelephoto end in the second embodiment;

FIGS. 14A, 14B, and 14C are diagrams showing the aberration at thewide-angle end in the third embodiment;

FIGS. 15A, 15B, and 15C are diagrams showing the aberration at themiddle focal length in the third embodiment;

FIGS. 16A, 16B, and 16C are diagrams showing the aberration at thetelephoto end in the third embodiment;

FIGS. 17A, 17B, and 17C are diagrams showing the aberration at thewide-angle end in the fourth embodiment;

FIGS. 18A, 18B, and 18C are diagrams showing the aberration at themiddle focal length in the fourth embodiment;

FIGS. 19A, 19B, and 19C are diagrams showing the aberration at thetelephoto end in the fourth embodiment;

FIGS. 20A, 20B, and 20C are diagrams showing the aberration at thewide-angle end in the fifth embodiment;

FIGS. 21A, 21B, and 21C are diagrams showing the aberration at themiddle focal length in the fifth embodiment;

FIGS. 22A, 22B, and 22C are diagrams showing the aberration at thetelephoto end in the fifth embodiment;

FIGS. 23A, 23B, and 23C are diagrams showing the aberration at thewide-angle end in the sixth embodiment;

FIGS. 24A, 24B, and 24C are diagrams showing the aberration at themiddle focal length in the sixth embodiment;

FIGS. 25A, 25B, and 25C are diagrams showing the aberration at thetelephoto end in the sixth embodiment;

FIGS. 26A, 26B, and 26C are diagrams showing the aberration at thewide-angle end in the seventh embodiment;

FIGS. 27A, 27B, and 27C are diagrams showing the aberration at themiddle focal length in the seventh embodiment;

FIGS. 28A, 28B, and 28C are diagrams showing the aberration at thetelephoto end in the seventh embodiment;

FIG. 29 is a diagram showing the lens construction of the zoom lenssystem of the eighth embodiment of the present invention;

FIG. 30 is a diagram showing the lens construction of the zoom lenssystem of the ninth embodiment of the present invention;

FIG. 31 is a diagram showing the lens construction of the zoom lenssystem of the tenth embodiment of the present invention;

FIG. 32 is a diagram showing the lens construction of the zoom lenssystem of the eleventh embodiment of the present invention;

FIG. 33 is a diagram showing the lens construction of the zoom lenssystem of the twelfth embodiment of the present invention;

FIGS. 34A, 34B, and 34C are diagrams showing the aberration at thewide-angle end in the eighth embodiment;

FIGS. 35A, 35B, and 35C are diagrams showing the aberration at themiddle focal length in the eighth embodiment;

FIGS. 36A, 36B, and 36C are diagrams showing the aberration at thetelephoto end in the eighth embodiment;

FIGS. 37A, 37B, and 37C are diagrams showing the aberration at thewide-angle end in the ninth embodiment;

FIGS. 38A, 38B, and 38C are diagrams showing the aberration at themiddle focal length in the ninth embodiment;

FIGS. 39A, 39B, and 39C are diagrams showing the aberration at thetelephoto end in the ninth embodiment;

FIGS. 40A, 40B, and 40C are diagrams showing the aberration at thewide-angle end in the tenth embodiment;

FIGS. 41A, 41B, and 41C are diagrams showing the aberration at themiddle focal length in the tenth embodiment;

FIGS. 42A, 42B, and 42C are diagrams showing the aberration at thetelephoto end in the tenth embodiment;

FIGS. 43A, 43B, and 43C are diagrams showing the aberration at thewide-angle end in the eleventh embodiment;

FIGS. 44A, 44B, and 44C are diagrams showing the aberration at themiddle focal length in the eleventh embodiment;

FIGS. 45A, 45B, and 45C are diagrams showing the aberration at thetelephoto end in the eleventh embodiment;

FIGS. 46A, 46B, and 46C are diagrams showing the aberration at thewide-angle end in the twelfth embodiment;

FIGS. 47A, 47B, and 47C are diagrams showing the aberration at themiddle focal length in the twelfth embodiment;

FIGS. 48A, 48B, and 48C are diagrams showing the aberration at thetelephoto end in the twelfth embodiment;

FIG. 49 is a diagram showing the lens construction of the zoom lenssystem of the thirteenth embodiment of the present invention;

FIG. 50 is a diagram showing the lens construction of the zoom lenssystem of the fourteenth embodiment of the present invention;

FIG. 51 is a diagram showing the lens construction of the zoom lenssystem of the fifteenth embodiment of the present invention;

FIG. 52 is a diagram showing the lens construction of the zoom lenssystem of the sixteenth embodiment of the present invention;

FIG. 53 is a diagram showing the lens construction of the zoom lenssystem of the seventeenth embodiment of the present invention;

FIG. 54 is a diagram showing the lens construction of the zoom lenssystem of the eighteenth embodiment of the present invention;

FIGS. 55A, 55B, and 55C are diagrams showing the aberration at thewide-angle end in the thirteenth embodiment;

FIGS. 56A, 56B, and 56C are diagrams showing the aberration at themiddle focal length in the thirteenth embodiment;

FIGS. 57A, 57B, and 57C are diagrams showing the aberration at thetelephoto end in the thirteenth embodiment;

FIGS. 58A, 58B, and 58C are diagrams showing the aberration at thewide-angle end in the fourteenth embodiment;

FIGS. 59A, 59B, and 59C are diagrams showing the aberration at themiddle focal length in the fourteenth embodiment;

FIGS. 60A, 60B, and 60C are diagrams showing the aberration at thetelephoto end in the fourteenth embodiment;

FIGS. 61A, 61B, and 61C are diagrams showing the aberration at thewide-angle end in the fifteenth embodiment;

FIGS. 62A, 62B, and 62C are diagrams showing the aberration at themiddle focal length in the fifteenth embodiment;

FIGS. 63A, 63B, and 63C are diagrams showing the aberration at thetelephoto end in the fifteenth embodiment;

FIGS. 64A, 64B, and 64C are diagrams showing the aberration at thewide-angle end in the sixteenth embodiment;

FIGS. 65A, 65B, and 65C are diagrams showing the aberration at themiddle focal length in the sixteenth embodiment;

FIGS. 66A, 66B, and 66C are diagrams showing the aberration at thetelephoto end in the sixteenth embodiment;

FIGS. 67A, 67B, and 67C are diagrams showing the aberration at thewide-angle end in the seventeenth embodiment;

FIGS. 68A, 68B, and 68C are diagrams showing the aberration at themiddle focal length in the seventeenth embodiment;

FIGS. 69A, 69B, and 69C are diagrams showing the aberration at thetelephoto end in the seventeenth embodiment;

FIGS. 70A, 70B, and 70C are diagrams showing the aberration at thewide-angle end in the eighteenth embodiment;

FIGS. 71A, 71B, and 71C are diagrams showing the aberration at themiddle focal length in the eighteenth embodiment;

FIGS. 72A, 72B, and 72C are diagrams showing the aberration at thetelephoto end in the eighteenth embodiment;

FIG. 73 is a diagram showing the lens construction of the zoom lenssystem of the nineteenth embodiment of the present invention;

FIG. 74 is a diagram showing the lens construction of the zoom lenssystem of the twentieth embodiment of the present invention;

FIG. 75 is a diagram showing the lens construction of the zoom lenssystem of the twenty-first embodiment of the present invention;

FIGS. 76A, 76B, and 76C are diagrams showing the aberration at thewide-angle end in the nineteenth embodiment;

FIGS. 77A, 77B, and 77C are diagrams showing the aberration at themiddle focal length in the nineteenth embodiment;

FIGS. 78A, 78B, and 78C are diagrams showing the aberration at thetelephoto end in the nineteenth embodiment;

FIGS. 79A, 79B, and 79C are diagrams showing the aberration at thewide-angle end in the twentieth embodiment;

FIGS. 80A, 80B, and 80C are diagrams showing the aberration at themiddle focal length in the twentieth embodiment;

FIGS. 81A, 81B, and 81C are diagrams showing the aberration at thetelephoto end in the twentieth embodiment;

FIGS. 82A, 82B, and 82C are diagrams showing the aberration at thewide-angle end in the twenty-first embodiment;

FIGS. 83A, 83B, and 83C are diagrams showing the aberration at themiddle focal length in the twenty-first embodiment;

FIGS. 84A, 84B, and 84C are diagrams showing the aberration at thetelephoto end in the twenty-first embodiment;

FIG. 85 is a diagram showing the lens construction of the zoom lenssystem of the twenty-second embodiment of the present invention;

FIG. 86 is a diagram showing the lens construction of the zoom lenssystem of the twenty-third embodiment of the present invention;

FIG. 87 is a diagram showing the lens construction of the zoom lenssystem of the twenty-fourth embodiment of the present invention;

FIGS. 88A, 88B, and 88C are diagrams showing the aberration at thewide-angle end in the twenty-second embodiment;

FIGS. 89A, 89B, and 89C are diagrams showing the aberration at themiddle focal length in the twenty-second embodiment;

FIGS. 90A, 90B, and 90C are diagrams showing the aberration at thetelephoto end in the twenty-second embodiment;

FIGS. 91A, 91B, and 91C are diagrams showing the aberration at thewide-angle end in the twenty-third embodiment;

FIGS. 92A, 92B, and 92C are diagrams showing the aberration at themiddle focal length in the twenty-third embodiment;

FIGS. 93A, 93B, and 93C are diagrams showing the aberration at thetelephoto end in the twenty-third embodiment;

FIGS. 94A, 94B, and 94C are diagrams showing the aberration at thewide-angle end in the twenty-fourth embodiment;

FIGS. 95A, 95B, and 95C are diagrams showing the aberration at themiddle focal length in the twenty-fourth embodiment; and

FIGS. 96A, 96B, and 96C are diagrams showing the aberration at thetelephoto end in the twenty-fourth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the zoom lens system of the present invention will bedescribed with reference to the drawings. Note that, in the followingdescriptions, the power with which a diffractive optical elementdiffracts light is referred to as the power of the diffractive opticalelement, and the composition of the power with which a diffractiveoptical element diffracts light and the refractive powers of individualrefractive optical surfaces is referred to as the composite power of thediffractive optical element and the refractive optical surfaces.

The zoom lens systems of the first to twenty-first embodiments of thepresent invention will be described below. The zoom lens system of eachembodiment is constituted of, from the object side, a first lens unitGr1 having a positive refractive power and a second lens unit Gr2 havinga negative refractive power. During zooming from the wide-angle end tothe telephoto end, the first and second lens units Gr1 and Gr2 are movedin such a way that the distance between them decreases. In each figureshowing the lens construction, the arrows m1 and m2 schematically showthe directions in which the first and second lens units Gr1 and Gr2 arerespectively moved during zooming from the wide-angle end (W) to thetelephoto end (T).

FIGS. 1 to 7 show the lens constructions of the zoom lens systems of thefirst to seventh embodiments. Each figure shows the lens construction atthe wide-angle end (W). In FIGS. 1 to 7, ri (i=1, 2, 3, . . . )represents the i-th surface from the object side, and di (i=1, 2, 3, . .. ) represents the i-th axial distance from the object side. A surfaceri marked with an asterisk (*) is an aspherical surface, and a surfaceri marked with (DOE) is a diffractive optical surface.

The zoom lens system of the first embodiment is constituted of, from theobject side, a first lens unit Gr1 composed of a light-shielding memberF, an aperture diaphragm A, and a positive meniscus lens element L1(having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) with its concave surface facingtoward the object side, and a second lens unit Gr2 composed only of anegative meniscus lens element L2 (having aspherical surfaces on bothsides and a diffractive optical element on the image-surface side) withits convex surface facing toward the object side.

The zoom lens system of the second embodiment is constituted of, fromthe object side, a first lens unit Gr1 composed of a light-shieldingmember F, an aperture diaphragm A, and a positive meniscus lens elementL1 (having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) with its concave surface facingtoward the object side, and a second lens unit Gr2 composed only of anegative meniscus lens element L2 (having aspherical surfaces on bothsides and a diffractive optical element on the image-surface side) withits convex surface facing toward the object side.

The zoom lens system of the third embodiment is constituted of, from theobject side, a first lens unit Gr1 composed of a light-shielding memberF, an aperture diaphragm A, and a positive meniscus lens element L1(having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) with its concave surface facingtoward the object side, and a second lens unit Gr2 composed only of anegative meniscus lens element L2 (having aspherical surfaces on bothsides and a diffractive optical element on the image-surface side) withits convex surface facing toward the object side.

The zoom lens system of the fourth embodiment is constituted of, fromthe object side, a first lens unit Gr1 composed of a light-shieldingmember F, an aperture diaphragm A, and a positive meniscus lens elementL1 (having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) with its concave surface facingtoward the object side, and a second lens unit Gr2 composed only of anegative meniscus lens element L2 (having aspherical surfaces on bothsides and a diffractive optical element on the image-surface side) withits convex surface facing toward the object side.

The zoom lens system of the fifth embodiment is constituted of, from theobject side, a first lens unit Gr1 composed of a light-shielding memberF, an aperture diaphragm A, and a positive meniscus lens element L1(having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) with its concave surface facingtoward the object side, and a second lens unit Gr2 composed only of anegative meniscus lens element L2 (having aspherical surfaces on bothsides) with its convex surface facing toward the object side.

The zoom lens system of the sixth embodiment is constituted of, from theobject side, a first lens unit Gr1 composed of a light-shielding memberF, an aperture diaphragm A, and a positive meniscus lens element L1(having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) made of plastics with its concavesurface facing toward the object side, and a second lens unit Gr2composed only of a negative meniscus lens element L2 (having asphericalsurfaces on both sides and a diffractive optical element on theimage-surface side) made of plastics with its convex surface facingtoward the object side.

The zoom lens system of the seventh embodiment is constituted of, fromthe object side, a first lens unit Gr1 composed of a light-shieldingmember F, an aperture diaphragm A, and a positive meniscus lens elementL1 (having aspherical surfaces on both sides and a diffractive opticalelement on the image-surface side) with its concave surface facingtoward the object side, and a second lens unit Gr2 composed only of abiconcave lens element L2 (having aspherical surfaces on both sides anda diffractive optical element on the image-surface side) made ofplastics.

To make a zoom lens system compact, it is necessary to shorten its totallength at the telephoto end. The zoom lens systems of the first toseventh embodiments are designed to be a telephoto-oriented zoom lenssystem by arranging a negative lens unit at the image-surface-side end.As a result, it is possible to realize a compact zoom lens system with arelatively short total length at the telephoto end.

Moreover, the zoom lens systems of the first to seventh embodiments areprovided with a diffractive optical element. The use of at least onediffractive optical element in a zoom lens system makes it possible toproperly correct chromatic aberration, which is difficult to correct ina conventional zoom lens system composed solely of refractive opticalelements when the number of optical elements is reduced to a minimum.

Next, FIGS. 29 to 33 show the lens constructions of the zoom lenssystems of the eighth to twelfth embodiments. Each figure shows the lensconstruction at the wide-angle end (W). In FIGS. 29 to 33, ri (i=1, 2,3, . . . ) represents the i-th surface from the object side, and di(i=1, 2, 3, . . . ) represents the i-th axial distance from the objectside. A surface ri marked with an asterisk (*) is an aspherical surface,and a surface ri marked with [DOE] is a diffractive optical surface.

The zoom lens system of the eighth embodiment is constituted of, fromthe object side, a first lens unit Gr1 composed of a first lens elementL1 (having aspherical surfaces on both sides) that is a negativemeniscus lens with its concave surface facing toward the object side, asecond lens element L2 that is a biconvex lens, and an aperturediaphragm A, and a second lens unit Gr2 composed of a third lens elementL3 (having aspherical surfaces on both sides and a diffractive opticalelement on the object side, and made of plastics) that is a positivemeniscus lens with its convex surface facing toward the image side, anda fourth lens element L4 that is a negative meniscus lens with itsconcave surface facing toward the object side.

The zoom lens system of the ninth embodiment is constituted of, from theobject side, a first lens unit Gr1 composed of a first lens element L1(having aspherical surfaces on both sides and a diffractive opticalelement on the object side) that is a negative meniscus lens with itsconvex surface facing toward the object side, a second lens element L2that is a positive meniscus lens with its convex surface facing towardthe image side, and an aperture diaphragm A, and a second lens unit Gr2composed of a third lens element L3 (having aspherical surfaces on bothsides) that is a positive meniscus lens with its convex surface facingtoward the image side, and a fourth lens element L4 that is a negativemeniscus lens with its concave surface facing toward the object side.

The zoom lens system of the tenth embodiment is constituted of, from theobject side, a first lens unit Gr1 composed of a first lens element L1(having aspherical surfaces on both sides) that is a negative meniscuslens with its convex surface facing toward the object side, a secondlens element L2 (having a diffractive optical element on theimage-surface side, and made of plastics) that is a biconvex lens, andan aperture diaphragm A, and a second lens unit Gr2 composed of a thirdlens element L3 (having aspherical surfaces on both sides and adiffractive optical element on the object side) that is a positivemeniscus lens with its convex surface facing toward the image side, anda fourth lens element L4 that is a negative meniscus lens with itsconcave surface facing toward the object side.

The zoom lens system of the eleventh embodiment is constituted of, fromthe object side, a first lens unit Gr1 composed of a first lens elementL1 (having an aspherical surface on the object side and a diffractiveoptical element on the object side) that is a negative meniscus lenswith its convex surface facing toward the object side, a second lenselement L2 that is a biconvex lens, and an aperture diaphragm A, and asecond lens unit Gr2 composed of a third lens element L3 (having anaspherical surface on the image side) that is a positive meniscus lenswith its convex surface facing toward the image side, and a fourth lenselement L4 that is a negative meniscus lens with its concave surfacefacing toward the object side.

The zoom lens system of the twelfth embodiment is constituted of, fromthe object side, a first lens unit Gr1 composed of a first lens elementL1 (having aspherical surfaces on both sides) that is a negativemeniscus lens with its convex surface facing toward the object side, asecond lens element L2 (having a diffractive optical element on theimage side) that is a biconvex lens, and an aperture diaphragm, and asecond lens unit Gr2 composed of a third lens element L3 (havingaspherical surfaces on both sides) that is a positive meniscus lens withits convex surface facing toward the image side, and a fourth lenselement L4 (having a diffractive optical element on the image side) thatis a negative meniscus lens with its concave surface facing toward theobject side.

In the zoom lens systems of the eighth to twelfth embodiments, the firstlens unit Gr1 is composed of two lens elements. When the first lens unitGr1 is composed of at least two lens elements, it is possible toproperly correct off-axial coma aberration, which occurs in the firstlens unit Gr1 when the whole system is adapted to high magnifications.

Moreover, the zoom lens systems of the eighth to twelfth embodiments areeach provided with a diffractive optical element. The use of at leastone diffractive optical element in a zoom lens system makes it possibleto properly correct chromatic aberration, which is difficult to correctin a conventional zoom lens system composed solely of refractive opticalsurfaces.

FIGS. 49 to 54 show the lens constructions of the zoom lens systems ofthe thirteenth to eighteenth embodiments. Each figure shows the lensconstruction at the wide-angle end (W). In FIGS. 49 to 54, ri (i=1, 2,3, . . . ) represents the i-th surface from the object side, and di(i=1, 2, 3, . . . ) represents the i-th axial distance from the objectside. A surface ri marked with an asterisk (*) is an aspherical surface,and a surface ri marked with [DOE] is a diffractive optical surface.

In the thirteenth embodiment, the first lens unit Gr1 is composed of,from the object side, a negative meniscus lens element (havingaspherical surfaces on both sides and a diffractive optical element onthe image side) with its convex surface facing toward the object side, abiconvex positive lens element, and an aperture diaphragm A. The secondlens unit Gr2 is composed of a negative meniscus lens element (havingaspherical surfaces on both sides) with its convex surface facing towardthe image side.

In the fourteenth embodiment, the first lens unit Gr1 is composed of,from the object side, a negative meniscus lens element (havingaspherical surfaces on both sides and a diffractive optical element onthe image side) with its convex surface facing toward the object side, apositive meniscus lens element with its concave surface facing towardthe object side, and an aperture diaphragm A. The second lens unit Gr2is composed of a negative meniscus lens element (having asphericalsurfaces on both sides and a diffractive optical element on the objectside) with its convex surface facing toward the image side.

In the fifteenth embodiment, the first lens unit Gr1 is composed of,from the object side, a negative meniscus lens element (havingaspherical surfaces on both sides) with its convex surface facing towardthe object side, a positive meniscus lens element with its concavesurface facing toward the object side, and an aperture diaphragm A. Thesecond lens unit Gr2 is composed of a negative meniscus lens element(having aspherical surfaces on both sides and a diffractive opticalelement on the object side) with its convex surface facing toward theimage side.

In the sixteenth embodiment, the first lens unit Gr1 is composed of,from the object side, a negative meniscus lens element (havingaspherical surfaces on both sides) with its concave surface facingtoward the object side, a biconvex positive lens element, and anaperture diaphragm A. The second lens unit Gr2 is composed of a negativemeniscus lens element (having aspherical surfaces on both sides and adiffractive optical element on the object side) with its convex surfacefacing toward the image side.

In the seventeenth embodiment, the first lens unit Gr1 is composed of,from the object side, a negative meniscus lens element (havingaspherical surfaces on both sides) with its concave surface facingtoward the object side, a biconvex positive lens element, and anaperture diaphragm A. The second lens unit Gr2 is composed of a negativemeniscus lens element (having aspherical surfaces on both sides and adiffractive optical element on the object side) with its convex surfacefacing toward the image side.

In the eighteenth embodiment, the first lens unit Gr1 is composed of,from the object side, a negative meniscus lens element (havingaspherical surfaces on both sides) with its concave surface facingtoward the object side, a positive meniscus lens element (having adiffractive optical element on the image side) with its concave surfacefacing toward the object side, and an aperture diaphragm A. The secondlens unit Gr2 is composed of a negative meniscus lens element (havingaspherical surfaces on both sides) with its convex surface facing towardthe image side.

As described above, in the zoom lens systems of the thirteenth toeighteenth embodiments, the first lens unit Gr1 is composed of two lenselements. When the first lens unit Gr1 is composed of at least two lenselements, it is possible to properly correct the off-axial comaaberration occurring in the first lens unit Gr1. Although the secondlens unit Gr2 is composed of one lens element, such reduction in thenumber of lens elements does not result here in undercorrection ofchromatic aberration as experienced in a conventional zoom lens systemcomposed solely of refractive optical surfaces. This is because the useof at least one diffractive optical element within the whole zoom lenssystem makes it possible to properly correct chromatic aberration. Notethat the only lens composing the second lens unit Gr2 may be either asingle lens or doublet lens.

FIGS. 73 to 75 show the lens constructions of the zoom lens systems ofthe nineteenth to twenty-first embodiments. Each figure shows the lensconstruction at the wide-angle end (W). In FIGS. 73 to 75, ri (i=1, 2,3, . . . ) represents the i-th surface from the object side, and di(i=1, 2, 3, . . . ) represents the i-th axial distance from the objectside. A surface ri marked with an asterisk (*) is an aspherical surface,and a surface ri marked with (DOE) is a diffractive optical surface.

In the nineteenth embodiment, the first lens unit Gr1 is composed of,from the object side, a positive meniscus lens element (havingaspherical surfaces on both sides and a diffractive optical element onthe image side) with its concave surface facing toward the object side,and an aperture diaphragm A. The second lens unit Gr2 is composed of,from the object side, a positive meniscus lens element (havingaspherical surfaces on both sides) with its convex surface facing towardthe image side, and a negative meniscus lens element with its concavesurface facing toward the object side.

In the twentieth embodiment, the first lens unit Gr1 is composed of,from the object side, a positive meniscus lens element (havingaspherical surfaces on both sides and a diffractive optical element onthe image side) with its concave surface facing toward the object side,and an aperture diaphragm A. The second lens unit Gr2 is composed of,from the object side, a positive meniscus lens element (havingaspherical surfaces on both sides) with its convex surface facing towardthe image side, and a negative meniscus lens element with its concavesurface facing toward the object side.

In the twenty-first embodiment, the first lens unit Gr1 is composed of,from the object side, a positive meniscus lens element (havingaspherical surfaces on both sides and a diffractive optical element onthe image side) with its concave surface facing toward the object side,and an aperture diaphragm A. The second lens unit Gr2 is composed of,from the object side, a positive meniscus lens element (havingaspherical surfaces on both sides and a diffractive optical element onthe image side) with its convex surface facing toward the image side,and a negative meniscus lens element with its concave surface facingtoward the object side.

As described above, in the zoom lens systems of the nineteenth totwenty-first embodiments, the first lens unit Gr1 is composed of onelens element, and the second lens unit Gr2 is composed of two lenselements. Composing the first lens unit Gr1 of one lens element makes itpossible to simplify the construction of the lens barrel, and also toreduce the size and cost of the zoom lens system. Composing the secondlens unit Gr2 of at least two lens elements makes it possible toproperly correct off-axial coma aberration. Although the first lens unitGr1 is composed of one lens element, such reduction in the number oflens elements does not result here in undercorrection of chromaticaberration as experienced in a conventional zoom lens system composedsolely of refractive optical surfaces. This is because the use of atleast one diffractive optical element within the whole zoom lens systemmakes it possible to properly correct chromatic aberration. Note thatthe only lens composing the first lens unit Gr1 may be either a singlelens or doublet lens.

In general, axial chromatic aberration, as dealt with in a thin-lenssystem, is defined by the following formula:

L=φr/νr+φdoe/νdoe  (A)

where

L: axial chromatic aberration;

φr: refractive power of the refractive optical surface;

νr: dispersion of the refractive optical surface (i.e. Abbe number);

φdoe: power of the diffractive optical element;

νdoe: dispersion of the diffractive optical element (i.e. the valuecorresponding to the Abbe number).

Furthermore, vr and vdoe above are defined by the following formulae:

νr=(Nd−1)/(Nf−Nc)  (B)

νdoe=λd/(λf−λc)=−3.45  (C)

where

Nd: refractive index of the refractive optical surface on the lensoptical axis, with d-lines;

Nf: refractive index of the refractive optical surface on the lensoptical axis, with f-lines;

Nc: refractive index of the refractive optical surface on the lensoptical axis, with c-lines;

λd: wavelength of d-lines;

λf: wavelength of f-lines;

λc: wavelength of c-lines.

Formula (C) above shows that a diffractive optical element has a largenegative value of dispersion (−3.45). By use of a diffractive opticalelement in combination with a refractive optical surface, the positiveφr/νr is canceled out by the negative φdoe/νdoe, and thus the chromaticaberration occurring in the refractive optical surface is corrected bythe diffractive optical element. The zoom lens systems of the first totwenty-first embodiments take advantage of this property of adiffractive optical element to correct chromatic aberration, bycorrecting the chromatic aberration occurring in a refractive opticalelement having a refractive optical surface by means of a diffractiveoptical element having a diffractive optical surface.

Furthermore, in the zoom lens systems of the first to twenty-firstembodiments, a diffractive optical element is provided on a refractiveoptical surface (as a hybrid diffractive-refractive lens element).Accordingly, the chromatic aberration occurring on the refractiveoptical surface can be properly corrected by the diffractive opticalelement. Moreover, the zoom lens systems of the first to twenty-firstembodiments can be made compact, since they need no additional lenselement for correcting chromatic aberration.

It is desirable, as in the first to twenty-first embodiments, that adiffractive optical element be provided on a refractive optical surfacehaving an aspherical shape. The use of an aspherical surface as a basesurface on which a diffractive optical element is provided allows theaspherical surface and the diffractive optical element to be shapedsimultaneously when, for example, the diffractive optical element isformed by machining. This not only leads to reduction of productiontime, but also permits high-precision machining. Therefore, providing adiffractive optical element on a refractive optical surface is highlyeffective in terms of production. Moreover, in a zoom lens system with areduced number of lens elements, it is necessary to correct sphericalaberration and coma aberration by use of an aspherical surface, andthese types of aberration can better be corrected with an asphericalbase surface for the diffractive optical element than with a sphericalone.

The phase shape of a diffractive optical element can be freely designed,and therefore it is possible to design a diffractive optical elementthat is optically equivalent to an aspherical surface on a refractiveoptical surface. Accordingly, not only chromatic aberration but alsospherical aberration can be corrected with a diffractive opticalelement. However, when spherical aberration is corrected solely with thephase shape of a diffractive optical element, the spherical aberrationfor light having a design wavelength is corrected, but, since lighthaving wavelengths different from the design value is diffracteddifferently, spherical aberration of color becomes rather greater. Forthis reason, it is preferable to correct spherical aberration with arefractive optical surface. In the first to twenty-first embodiments,spherical aberration and off-axial coma aberration are correctedproperly with an aspherical surface of a refractive optical surface,whereas axial chromatic aberration and chromatic aberration ofmagnification are corrected with a diffractive optical element providedon a refractive optical surface, so that satisfactory opticalperformance is obtained.

It is desirable that the diffractive optical element be blazed(saw-toothed). With a blazed diffractive optical element, it is possibleto obtain better diffraction efficiency. A blazed diffractive opticalelement can be produced by approximating the saw-toothed shape as astepped shape in a manner similar to a semiconductor productiontechnique (binary optics), or by molding glass or a plastic materialwith a mold produced through precision machining, or by molding a resinlayer formed on the surface of a glass lens into a diffractive opticalelement.

In the zoom lens systems of the first to fourth, sixth, and seventhembodiments, a diffractive optical element is arranged in the secondlens unit. The use of at least one diffractive optical element in thenegative lens unit that is disposed at the image-surface-side end makesit possible to properly correct the chromatic aberration ofmagnification occurring in the object-side lens unit.

Moreover, in the zoom lens systems of the first to seventh embodiments,a diffractive optical element is arranged in the first lens unit havinga positive refractive power. The use of at least one diffractive opticalelement in the lens unit that is disposed at the object-side end makesit possible to properly correct the axial chromatic aberration occurringin the object-side lens unit having a positive refractive power as awhole.

Of the first to seventh embodiments, the zoom lens systems of the sixthand seventh embodiments have a diffractive optical element provided on aplastic lens element, and therefore these zoom lens systems can beproduced with especially reduced cost.

Moreover, the zoom lens systems of the first to seventh embodiments isconstituted of, from the object side, a first lens unit having apositive refractive power and a second lens unit having a negativerefractive power, and, during zooming from the wide-angle end to thetelephoto end, the first and second lens units are moved in such a waythat the distance between them decreases. Generally, in a zoom lenssystem for a lens shutter camera having a magnification around 2×,adoption of a two-lens-unit construction constituted of the positive andnegative lens units helps produce a compact zoom lens system withsatisfactory optical performance.

In the zoom lens systems of the first to seventh embodiments, the use ofa diffractive optical element in a zoom lens system constituted of twopositive and negative lens units makes it possible to properly correctchromatic aberration, which cannot be corrected satisfactorily withrefractive optical surfaces alone, and also to reduce the number of lenselements needed.

It is preferable that the zoom lens systems of the first to seventhembodiments satisfy the following conditional expression (1):

0.01<|φdoe/φr|<0.12  (1)

where

φdoe: power of the diffractive optical element;

φr: composite power of the diffractive optical element and therefractive optical surface.

If the upper limit of conditional expression (1), is exceeded, the powerof the diffractive optical element within the lens unit is too strong,with the result that chromatic aberration is overcorrected by thediffractive optical element. By contrast, if the lower limit ofconditional expression (1) is exceeded, the power of the diffractiveoptical element within the lens unit is too weak, with the result thatchromatic aberration is undercorrected by the diffractive opticalelement.

Moreover, in the zoom lens systems of the first to seventh embodiments,it is preferable that the following conditional expression (2) besatisfied:

2<|R ₂ ×H _(max)/λ₀|<50  (2)

where

R₂: secondary phase coefficient of the diffractive optical element;

H_(max): effective radius of the diffractive optical element;

λ₀: design wavelength.

If the lower limit of conditional expression (2) is exceeded, thecorrection of chromatic aberration by the diffractive optical element isinsufficient, and accordingly it is difficult to correct chromaticaberration properly. By contrast, if the upper limit of conditionalexpression (2) is exceeded, not only the correction of chromaticaberration is excessive, but also the pitch of the diffractive opticalelement at its periphery becomes too small to obtain sufficientdiffraction effects. In addition, if the upper limit of conditionalexpression (2) is exceeded, and accordingly the pitch of the diffractiveoptical element becomes smaller, the diffractive optical element becomesmore difficult to produce.

Furthermore, it is preferable that the zoom lens systems of the first toseventh embodiments satisfy the following conditional expression (3):

0.9<|φGr 1/φGr 2|<1.7  (3)

where

φGr1: composite power of the first lens unit;

φGr2: composite power of the second lens unit.

If the upper limit of conditional expression (3) is exceeded, therefractive power of the second lens unit relative to that of the firstlens unit is too weak, with the result that the moving amount of thesecond lens unit during zooming from the wide-angle end to the telephotoend becomes larger. This is not effective in making the zoom lens systemcompact. By contrast, if the lower limit of conditional expression (3)is exceeded, the refractive power of the second lens unit relative tothat of the first lens unit is too strong, with the result that thePetzval sum becomes too great to a minus side to correct.

Incidentally, it is well-known that, in a zoom lens system constitutedof two positive and negative lens units, the effective radius of thesecond lens unit is generally greater than that of the first lens unit.Accordingly, in attempting to reduce the cost of the zoom lens systemconstituted of two positive and negative lens units by providing it witha diffractive optical element, it is more effective to provide thediffractive optical element only in the first lens unit, which has thesmaller effective radius. In the zoom lens system of the fifthembodiment, a diffractive optical element is provided only in the firstlens unit. This further reduces the production cost.

Moreover, in cases where the second lens unit is composed of one lenselement having only refractive optical surfaces as in the fifthembodiment, it is preferable that the following conditional expression(4) be satisfied:

ν21>44  (4)

where

ν21: dispersion of the refractive optical surface of the second lensunit.

When the second lens unit is composed of one lens element having onlyrefractive optical surfaces, it is nearly impossible to correctchromatic aberration within the lens unit. However, as long asconditional expression (4) is satisfied, chromatic aberration can becorrected properly over the whole lens system. If the dispersion is sogreat that the lower limit of conditional expression (4) is exceeded,the chromatic aberration of magnification occurring in the second lensunit is too great to correct properly.

In the zoom lens systems of the eighth and tenth embodiments, adiffractive optical element is provided in the second lens unit Gr2. Theuse of at least one diffractive optical element in the negative lensunit that is disposed at the image-surface-side end makes it possible toproperly correct the chromatic aberration of magnification occurring inthe object-side lens unit. In addition, the use of at least onediffractive optical element in a negative lens unit makes it possible toproperly correct axial chromatic aberration.

Moreover, in the zoom lens systems of the ninth and eleventhembodiments, a diffractive optical element is provided on theobject-side surface of the first lens element L1. The use of adiffractive optical element at the object-side end, where light pathsvary greatly with the angle of view, makes it possible to properlycorrect axial chromatic aberration and off-axial chromatic aberration ofmagnification.

Moreover, in the zoom lens systems of the eighth and tenth embodiments,a diffractive optical element is arranged on the object-side surface ofthe third lens element L3. The use of a diffractive optical element atthe object-side end of the second lens unit, where light paths varygreatly with the angle of view, makes it possible to properly correctoff-axial chromatic aberration of magnification.

Of the eighth to twelfth embodiments, the zoom lens systems of theeighth and tenth embodiments have a diffractive optical element formedon their third, plastic, lens element L3, and therefore these zoom lenssystems can be produced with especially reduced cost.

On the other hand, the use of a blazed diffractive optical elementcauses degradation of diffraction efficiency because, as the angle ofincidence becomes greater, the apparent pitch of the diffractive opticalelement as seen from the direction of incidence becomes smaller.However, this problem can be alleviated by disposing the diffractiveoptical element at the image-side end of a lens unit. For example, whena diffracting optical element is provided at the image-surface-side endof the first lens unit Gr1 as in the tenth and twelfth embodiments, theangle of incidence of light rays striking the diffractive opticalelement becomes smaller than at the object-side surface of the samelens, and thus degradation of diffraction efficiency is suppressed. Forthe same reason, it is also possible to provide a diffractive opticalelement at the image-surface-side end of the second lens unit Gr2 as inthe twelfth embodiment.

The conditions that need to be satisfied by the zoom lens systems of theeighth to twelfth embodiments will be described below.

It is preferable that the zoom lens systems of the eighth to twelfthembodiments satisfy the following conditional expression (5):

0.005<|φdoe/φr|<0.12  (5)

where

φdoe: power of the diffractive optical element;

φr: composite power of the diffractive optical element and therefractive optical surface.

If the upper limit of conditional expression (5) is exceeded, the powerof the diffractive optical element within the lens unit is too strong,with the result that chromatic aberration is overcorrected by thediffractive optical element. By contrast, if the lower limit ofconditional expression (5) is exceeded, the power of the diffractiveoptical element within the lens unit is too weak, with the result thatchromatic aberration is undercorrected by the diffractive opticalelement.

Moreover, in the zoom lens systems of the eighth to twelfth embodiments,it is preferable that the following conditional expression (6) besatisfied:

2<|R ₂ ×H _(max)/λ₀<57  (6)

where

R₂: secondary phase coefficient of the diffractive optical element;

H_(max): effective radius of the diffractive optical element;

λ₀: design wavelength.

If the lower limit of conditional expression (6) is exceeded, thecorrection of chromatic aberration by the diffractive optical element isinsufficient, and accordingly it is difficult to correct chromaticaberration properly. By contrast, if the upper limit of conditionalexpression (6) is exceeded, not only the correction of chromaticaberration is excessive, but also the pitch of the diffractive opticalelement at its periphery becomes too small to obtain sufficientdiffraction effects. In addition, as the pitch of the diffractiveoptical element becomes smaller, the diffractive optical element becomesmore difficult to produce.

It is desirable, as in the fourteenth to seventeenth embodiments, toprovide the second lens unit Gr2 with at least one diffractive opticalelement. The use of at least one diffractive optical element in thesecond lens unit Gr2 makes it possible, even if the second lens unit Gr2is composed of one lens element, to properly correct the chromaticaberration occurring in the second lens unit Gr2 and thus to reduce thechromatic aberration occurring during zooming.

Moreover, it is desirable, as in the thirteenth, fourteenth, andeighteenth embodiments, to provide the first lens unit Gr1 with at leastone diffractive optical element. The use of at least one diffractiveoptical element in the first lens unit Gr1 makes it possible to properlycorrect axial chromatic aberration.

In a zoom lens system consisting of two, positive and negative, lensunits, such as the thirteenth to eighteenth embodiments described above,in which at least one diffractive optical element is provided within thewhole system and in which, during zooming from the wide-angle end (W) tothe telephoto end (T), a first lens unit Gr1 composed of at least twolens elements and a second lens unit Gr2 composed of one lens elementare moved in such a way that the distance (d5) between them decreases,it is desirable that each lens unit that is provided with a diffractiveoptical element satisfy the following conditional expression (7):

0.01<|φdoe/φr|<0.09  (7)

where

φdoe: power of the diffractive optical element;

φr: composite power of the diffractive optical element and therefractive optical surface.

If the upper limit of conditional expression (7) is exceeded, the powerof the diffractive optical element within the lens unit is too strong,with the result that chromatic aberration is overcorrected by thediffractive optical element. By contrast, if the lower limit ofconditional expression (7) is exceeded, the power of the diffractiveoptical element within the lens unit is too weak, with the result thatchromatic aberration is undercorrected by the diffractive opticalelement.

Furthermore, it is desirable that the following conditional expression(8), which is the same as the above-described conditional expression(2), be satisfied:

2<|R ₂ ×H _(max)/λ₀|<50  (8)

Conditional expression (8) defines the range of conditions to bepreferably satisfied in the production of the diffractive opticalelement. If the lower limit of conditional expression (8) is exceeded,the correction of chromatic aberration by the diffractive opticalelement is insufficient, and accordingly it is difficult to correctchromatic aberration properly. By contrast, if the upper limit ofconditional expression (8) is exceeded, not only the correction ofchromatic aberration is excessive, but also the pitch of the diffractiveoptical element at its periphery becomes too small to obtain sufficientdiffraction effects. In addition, as the pitch of the diffractiveoptical element becomes smaller, the diffractive optical element becomesmore difficult to produce.

In a zoom lens system consisting of two, positive and negative, lensunits, such as the thirteenth, fourteenth, and eighteenth embodimentsdescribed above, in which at least one diffractive optical element isprovided in the first lens unit Gr1 and in which, during zooming fromthe wide-angle end (W) to the telephoto end (T), a first lens unit Gr1composed of at least two lens elements and a second lens unit Gr2composed of one lens are moved in such a way that the distance (d5)between them decreases, it is desirable that the following expression(9) be satisfied:

0.01<|φdoe1/φr 1|<0.05  (9)

where

φdoe1: power of the diffractive optical element provided in the firstlens unit Gr1;

φr1: composite power of the first lens element Gr1.

Conditional expression (9) defines, for the cases where a diffractiveoptical element is provided in the first lens unit Gr1, the desirablerange of the power of the diffractive optical element. If the upperlimit of conditional expression (9) is exceeded, the power of thediffractive optical element within the first lens unit Gr1 is toostrong, with the result that chromatic aberration is overcorrected bythe diffractive optical element. In addition, the pitch of thediffractive optical element becomes too small, which makes thediffractive optical element more difficult to produce. By contrast, ifthe lower limit of conditional expression (9) is exceeded, the power ofthe diffractive optical element within the first lens unit Gr1 is tooweak, with the result that chromatic aberration is undercorrected by thediffractive optical element. This leads to undercorrection of thechromatic aberration in the zoom lens system as a whole.

In a zoom lens system consisting of two, positive and negative, lensunits, such as the fourteenth to seventeenth embodiments describedabove, in which at least one diffractive optical element is provided inthe second lens unit Gr2 and in which, during zooming from thewide-angle end (W) to the telephoto end (T), a first lens unit Gr1composed of at least two lens elements and a second lens unit Gr2composed of one lens are moved in such a way that the distance (d5)between them decreases, it is desirable that the following expression(10) be satisfied:

0.01<|φdoe2/φr 2|<0.05  (10)

where

φdoe2: power of the diffractive optical element provided in the secondlens unit Gr2;

φr2: composite power of the second lens element Gr2.

Conditional expression (10) defines, for the cases where a diffractiveoptical element is provided in the second lens unit Gr2, the desirablerange of the power of the diffractive optical element. If the upperlimit of conditional expression (10) is exceeded, the power of thediffractive optical element within the second lens unit Gr2 is toostrong, with the result that chromatic aberration is overcorrected bythe diffractive optical element. In addition, the pitch of thediffractive optical element becomes too small, which makes thediffractive optical element more difficult to produce. By contrast, ifthe lower limit of conditional expression (10) is exceeded, the power ofthe diffractive optical element within the second lens unit Gr2 is tooweak, with the result that chromatic aberration is undercorrected by thediffractive optical element. This leads to undercorrection of thechromatic aberration in the zoom lens system as a whole.

It is desirable, as in the thirteenth to eighteenth embodiments, that adiffractive optical element be provided on the surface of a refractiveoptical element made of plastics (i.e. plastic lens element).Preferably, the first and second lens units Gr1 and Gr2 are composedsolely of plastic lens elements. A diffractive optical element can beformed on the surface of a plastic lens element, for example, byinjection-molding the two elements simultaneously. Accordingly, it ismore effective, in terms of cost reduction, to form a diffractiveoptical element on the surface of a plastic lens element, than on thesurface of a glass lens element.

It is desirable, as in the eighteenth embodiment, to provide adiffractive optical element at the image-side end of the first lens unitGr1. In general, in a construction where the aperture diaphragm A isdisposed between the first and second lens units Gr1 and Gr2, it is tobe noted, in considering the effectiveness of the surface on which adiffractive optical element is provided, that, within the first lensunit Gr1, a lens element closer to the object has a larger effectiveradius. Accordingly, by providing a diffractive optical element at theimage-side end of the first lens unit Gr1, it is possible to reduce theeffective radius of the diffractive optical element. This is quiteeffective in the production of the diffractive optical element.

It is desirable, as in the fourteenth to seventeenth embodiments, toprovide a diffractive optical element at the object-side end of thesecond lens element Gr2. In cases where a blazed diffractive opticalelement is used, as the angle of incidence of rays striking thediffractive optical element becomes greater, the apparent pitch of thediffractive optical element as seen from the direction of incidencebecomes smaller, thereby causing degradation of diffraction efficiency.By providing a diffractive optical element at the object-side end of thesecond lens element Gr2, it is possible to reduce the angle of incidenceof rays striking the diffractive optical element, as well as to reducethe variation of the angle of incidence during zooming. Thus,degradation of diffraction efficiency can be suppressed.

It is desirable, as in the nineteenth to twenty-first embodiments, toprovide at least one diffractive optical element in the first lens unitGr1. The use of at least one diffractive optical element in the firstlens unit Gr1 makes it possible, even if the first lens unit Gr1 iscomposed of one lens element, to properly correct the chromaticaberration occurring in the first lens unit Gr1.

Moreover, it is desirable, as in the twenty-first embodiment, to provideat least one diffractive optical element in the second lens unit Gr2.The use of at least one diffractive optical element in the second lensunit Gr2 makes it possible to properly correct chromatic aberration ofmagnification, and to reduce the chromatic aberration during zooming.

In a zoom lens system consisting of two, positive and negative, lensunits, such as the nineteenth to twenty-first embodiments describedabove, in which at least one diffractive optical element is providedwithin the whole system and in which, during zooming from the wide-angleend (W) to the telephoto end (T), a first lens unit Gr1 composed of onelens element and a second lens unit Gr2 composed of at least two lenselements are moved in such a way that the distance (d3) between themdecreases, it is desirable that each lens unit that is provided with adiffractive optical element satisfy the following conditional expression(11):

0.03<|φdoe/φr|<0.15  (11)

where

φdoe: power of the diffractive optical element;

φr: composite power of the diffractive optical element and therefractive optical surface.

If the upper limit of conditional expression (11) is exceeded, the powerof the diffractive optical element within the lens unit is too strong,with the result that chromatic aberration is overcorrected by thediffractive optical element. By contrast, if the lower limit ofconditional expression (11) is exceeded, the power of the diffractiveoptical element within the lens unit is too weak, with the result thatchromatic aberration is undercorrected by the diffractive opticalelement.

Furthermore, it is desirable that the following conditional expression(12) be satisfied:

2<|R ₁ ×H _(max)/λ₀|<25  (12)

where

R₂: secondary phase-function coefficient of the diffractive opticalelement;

H_(max): effective radius of the diffractive optical element;

λ₀: design wavelength.

Conditional expression (12) defines the range of conditions to bepreferably satisfied in the production of the diffractive opticalelement. If the lower limit of conditional expression (12) is exceeded,the correction of chromatic aberration by the diffractive opticalelement is insufficient, and accordingly it is difficult to correctchromatic aberration properly. By contrast, if the upper limit ofconditional expression (12) is exceeded, not only the correction ofchromatic aberration is excessive, but also the pitch of the diffractiveoptical element at its periphery becomes too small to obtain sufficientdiffraction effects. In addition, as the pitch of the diffractiveoptical element becomes smaller, the diffractive optical element becomesmore difficult to produce.

In a zoom lens system consisting of two, positive and negative, lensunits, such as the nineteenth to twenty-first embodiments describedabove, in which at least one diffractive optical element is provided inthe first lens unit Gr1 and in which, during zooming from the wide-angleend (W) to the telephoto end (T), a first lens unit Gr1 composed of onelens element and a second lens unit Gr2 composed of at least two lenselements are moved in such a way that the distance (d3) between themdecreases, it is desirable that the following conditional expression(13) be satisfied:

0.03<|φdoe1/φr 1|<0.10  (13)

where

φdoe1: power of the diffractive optical element provided in the firstlens unit Gr1;

φr1: composite power of the first lens element Gr1.

Conditional expression (13) defines, for the cases where a diffractiveoptical element is provided in the first lens unit Gr1, the desirablerange of the power of the diffractive optical element. If the upperlimit of conditional expression (13) is exceeded, the power of thediffractive optical element within the first lens unit Gr1 is toostrong, with the result that chromatic aberration is overcorrected bythe diffractive optical element. In addition, the pitch of thediffractive optical element becomes too small, which makes thediffractive optical element more difficult to produce. By contrast, ifthe lower limit of conditional expression (13) is exceeded, the power ofthe diffractive optical element within the first lens unit Gr1 is tooweak, with the result that chromatic aberration is undercorrected by thediffractive optical element. This leads to undercorrection of thechromatic aberration in the zoom lens system as a whole.

In a zoom lens system consisting of two, positive and negative, lensunits, such as the twenty-first embodiment described above, in which atleast one diffractive optical element is provided in the second lensunit Gr2 and in which, during zooming from the wide-angle end (W) to thetelephoto end (T), a first lens unit Gr1 composed of one lens elementand a second lens unit Gr2 composed of at least two lens elements aremoved in such a way that the distance (d3) between them decreases, it isdesirable that the following conditional expression (14) be satisfied:

0.06<|φdoe2/φr 2|<0.15  (14)

where

φdoe2: power of the diffractive optical element provided in the secondlens unit Gr2;

φr2: composite power of the second lens element Gr2.

Conditional expression (14) defines, for the cases where a diffractiveoptical element is provided in the second lens unit Gr2, the desirablerange of the power of the diffractive optical element. If the upperlimit of conditional expression (14) is exceeded, the power of thediffractive optical element within the second lens unit Gr2 is toostrong, with the result that chromatic aberration is overcorrected bythe diffractive optical element. In addition, the pitch of thediffractive optical element becomes too small, which makes thediffractive optical element more difficult to produce. By contrast, ifthe lower limit of conditional expression (14) is exceeded, the power ofthe diffractive optical element within the second lens unit Gr2 is tooweak, with the result that chromatic aberration is undercorrected by thediffractive optical element. This leads to undercorrection of thechromatic aberration in the zoom lens system as a whole.

It is desirable, as in the nineteenth to twenty-first embodiments, toprovide a diffractive optical element at the image-side end of the firstlens unit Gr1. In general, in a construction where the aperturediaphragm A is disposed between the first and second lens units Gr1 andGr2, it is to be noted, in considering the effectiveness of the surfaceon which a diffractive optical element is provided, that, within thefirst lens unit Gr1, a lens element closer to the object has a largereffective radius. Accordingly, by providing a diffractive opticalelement at the image-side end of the first lens unit Gr1, it is possibleto reduce the effective radius of the diffractive optical element. Thisis quite effective in the production of the diffractive optical element.

Table 1 to 7 below show the construction data of the zoom lens systemsof the first to seventh embodiments, respectively.

Table 9 to 13 below show the construction data of the zoom lens systemsof the eighth to twelfth embodiments, respectively.

Table 15 to 20 below show the construction data of the zoom lens systemsof the thirteenth to eighteenth embodiments, respectively.

Table 22 to 24 below show the construction data of the zoom lens systemsof the nineteenth to twenty-first embodiments, respectively.

In the construction data of each embodiment, ri (i=1, 2, 3, . . . )represents the curvature radius of the i-th surface from the objectside, di (i=1, 2, 3, . . . ) represents the i-th axial distance from theobject side, and Ni (i=1, 2, 3, . . . ) and νi (i=1, 2, 3, . . . )respectively represent the d-lines refractive coefficient and the Abbenumber of the i-th lens from the object side. Note that the letter Efound in numerical values listed on the tables indicates that thefigures following it represents an exponent. For example, 1.0E2represents 1.0×10².

Moreover, three values listed for the focal length f and the f-numberFNO of the whole system and for the distance between the first andsecond lens units (axial distance d5) are the values at, from left, thewide-angle end (W), the middle focal length (M), and the telephoto end(T).

In the construction data of each embodiment, a surface marked with anasterisk (*) in the curvature radius column is an aspherical surface.The surface shape of an aspherical surface is defined by the followingformula: $\begin{matrix}{Y = {\frac{C \cdot X^{2}}{1 + \left( {1 - {ɛ \cdot X^{2} \cdot C^{2}}} \right)^{1/2}} + {\sum\limits_{i}{AiX}^{i}}}} & (D)\end{matrix}$

where

X: height in the direction perpendicular to the optical axis;

Y: displacement from the reference surface of the optical axisdirection;

C: paraxial curvature;

ε: quadric surface parameter;

Ai: aspherical coefficient of the i-th order.

Moreover, in the construction data of each embodiment, a surface markedwith [DOE] in the curvature radius column is a surface where adiffractive optical element is provided on the surface of a refractiveoptical element. The phase shape of a diffractive optical element, whichdetermines the pitch of the diffractive optical element, is defined bythe following formula: $\begin{matrix}{{\varphi (X)} = {2{\pi \cdot {\left( {\sum\limits_{i}{\cdot {Ri} \cdot X^{i}}} \right)/\lambda_{0}}}}} & (E)\end{matrix}$

where

φ(X): phase function;

Ri: phase coefficient of the i-th order;

X: height in the direction perpendicular to the optical axis;

λ₀: design wavelength.

Moreover, the first to seventh embodiments satisfy conditionalexpressions (1) to (3) described above. In addition, the fifthembodiment also satisfies conditional expression (4). Table 8 lists thevalues corresponding to conditional expressions (1) to (3) in the firstto seventh embodiments, and the value of ν21 in the fifth embodiment.

Moreover, the eighth to twelfth embodiments satisfy conditionalexpressions (5) and (6) described above. Table 14 lists the valuescorresponding to conditional expressions (5) and (6) in the eighth totwelfth embodiments.

Moreover, the thirteenth to eighteenth embodiments satisfy conditionalexpressions (7) to (10) described above. Table 21 lists the valuescorresponding to conditional expressions (7) to (10) in the thirteenthto eighteenth embodiments.

Moreover, the nineteenth to twenty-first embodiments satisfy conditionalexpressions (11) to (14) described above. Table 25 lists the valuescorresponding to conditional expressions (11) to (14) in the nineteenthto twenty-first embodiments.

FIGS. 8A to 8C, 11A to 11C, 14A to 14C, 17A to 17C, 20A to 20C, 23A to23C and 26A to 26C show the aberration at the wide-angle end in thefirst to seventh embodiments, respectively. FIGS. 9A to 9C, 12A to 12C,15A to 15C, 18A to 18C, 21A to 21C, 24A to 24C, and 27A to 27C show theaberration at the middle focal length in the first to seventhembodiments, respectively. FIGS. 10A to 10C, 13A to 13C, 16A to 16C, 19Ato 19C, 22A to 22C, 25A to 25C, and 28A to 28C show t aberration at thetelephoto end in the first to seventh embodiments, respectively. FIGS.8A to 28A illustrate spherical aberration, FIGS. 8B to 28B illustrateastigmatism, and FIGS. 8C to 28C illustrate distortion.

FIGS. 34A to 34C, 37A to 37C, 40A to 40C, 43A to 43C, and 46A to 46Cshow the aberration at the wide-angle end in the eighth to twelfthembodiments, respectively. FIGS. 35A to 35C, 38A to 38C, 41A to 41C, 44Ato 44C, and 47A to 47C show the aberration at the middle focal length inthe eighth to twelfth embodiments, respectively. FIGS. 36A to 36C, 39Ato 39C, 42A to 42C, 45A to 45C, and 48A to 48C show the aberration atthe telephoto end in the eighth to twelfth embodiments, respectively.FIGS. 34A to 48A illustrate spherical aberration, FIGS. 34B to 48Billustrate astigmatism, and FIGS. 34C to 48C illustrate distortion.

FIGS. 55A to 55C, 58A to 58C, 61A to 61C, 64A to 64C, 67A to 67C, and70A to 70C show the aberration at the wide-angle end in the thirteenthto eighteenth embodiments, respectively. FIGS. 56A to 56C, 59A to 59C,62A to 62C, 65A to 65C, 68A to 68C, and 71A to 71C show the aberrationat the middle focal length in the thirteenth to eighteenth embodiments,respectively. FIGS. 57A to 57C, 60A to 60C, 63A to 63C, 66A to 66C, 69Ato 69C, and 72A to 72C show the aberration at the telephoto end in thethirteenth to eighteenth embodiments, respectively. FIGS. 55A to 72Aillustrate spherical aberration, FIGS. 55B to 72B illustrateastigmatism, and FIGS. 55C to 72C illustrate distortion.

FIGS. 76A to 76C, 79A to 79C, and 82A to 82C show the aberration at thewide-angle end in the nineteenth to twenty-first embodiments,respectively. FIGS. 77A to 77C, 80A to 80C, and 83A to 83C show theaberration at the middle focal length in the nineteenth to twenty-firstembodiments, respectively. FIGS. 78A to 78C, 81A to 81C, and 84A to 84Cshow the aberration at the telephoto end in the nineteenth totwenty-first embodiments, respectively. FIGS. 76A to 84A illustratespherical aberration, FIGS. 76B to 84B illustrate astigmatism, and FIGS.76C to 84C illustrate distortion.

In the spherical aberration diagrams, the solid line (d), broken line(c), and dash-dot line (g) show the aberration for d-lines (wavelength:λd=587.6 nm), c-lines (wavelength: λc=656.3 nm), and g-lines(wavelength: λg=435.8 nm), respectively. In the spherical aberrationdiagrams (horizontal axis: mm), the vertical axis represents h/h₀, whichis the height of incidence h standardized by its maximum height h₀. Inthe astigmatism diagrams (horizontal axis: mm) and the distortiondiagrams (horizontal axis: %), the vertical axis represents half theangle of view ω (°). Furthermore, in the astigmatism diagrams, the solidline M and the solid line S show astigmatism on the meridional surfaceand on the sagittal surface, respectively.

The zoom lens systems of the twenty-second to twenty-fourth embodimentsof the present invention will be described below.

FIG. 85 shows the lens construction of the zoom lens system of thetwenty-second embodiment, as observed at its wide-angle end (W). Thezoom lens system of the twenty-second embodiment is constituted of, fromthe object side, a first lens unit Gr1 having a positive power, a secondlens unit Gr2 having a positive power, and a third lens unit Gr3 havinga negative power and disposed at the image-side end of the zoom lenssystem. This zoom lens system performs zooming from the wide-angle end(W) to the telephoto end (T) by moving all the lens units toward theobject side in such a way that the distance between the first and secondlens units Gr1 and Gr2 increases and that the distance between thesecond and third lens units Gr2 and Gr3 decreases. In FIG. 85, thearrows m1 to m3 schematically indicate the movement of the first tothird lens units Gr1 to Gr3 from the wide-angle end [W] to the telephotoend [T].

The first lens unit Gr1 is composed of, from the object side, a firstlens element L1 formed as a negative meniscus lens element concave tothe object side, and a second lens element L2 formed as a positivemeniscus lens element convex to the object side. The second lens unitGr2 is composed of, from the object side, a third lens element L3 havinga negative power and having aspherical surfaces on both sides, and afourth lens element L4 formed as a positive meniscus lens elementconcave to the object side. The third lens unit Gr3 is composed solelyof a fifth lens element L5 formed as a biconcave lens element havingaspherical surfaces on both sides and having a diffractive opticalsurface on the object side. An aperture diaphragm S is provided betweenthe first and second lens units Gr1 and Gr2 so as to move together withthe second lens unit L2 during zooming.

FIG. 86 shows the lens construction of the zoom lens system of thetwenty-third embodiment, as observed at its wide-angle end [W]. The zoomlens system of the twenty-third embodiment is constituted of, from theobject side, a first lens unit Gr1 having a positive power, a secondlens unit Gr2 having a negative power, a third lens unit Gr3 having apositive power, and a fourth lens unit Gr4 having a negative power anddisposed at the image-side end of the zoom lens system. This zoom lenssystem performs zooming from the wide-angle end (W) to the telephoto end(T) by moving all the lens units toward the object side in such a waythat the distance between the first and second lens units Gr1 and Gr2increases, that the distance between the second and third lens units Gr2and Gr3 increases, and that the distance between the third and fourthlens units Gr3 and Gr4 decreases. In FIG. 86, the arrows m1 to m4schematically indicate the movement of the first to fourth lens unitsGr1 to Gr4 from the wide-angle end (W) to the telephoto end (T).

The first lens unit Gr1 is composed of, from the object side, a firstlens element L1 formed as a negative meniscus lens element convex to theobject side, and a second lens element L2 formed as a positive meniscuslens element convex to the object side. The second lens unit Gr2 iscomposed of, from the object side, a third lens element L3 formed as abiconcave lens element (having an aspherical surface on the objectside), and a fourth lens element L4 formed as a positive meniscus lenselement convex to the object side. The third lens unit Gr3 is composedof, from the object side, a fifth lens element L5 formed as a biconvexlens element, a sixth lens element L6 formed as a negative meniscus lenselement convex to the object side (having an aspherical surface on theobject side), and a seventh lens element L7 formed as a positive lenselement having a weakly powered surface on the object side. The fourthlens unit Gr4 is composed of, from the object side, an eighth lenselement L8 formed as a positive meniscus lens element concave to theobject side and having aspherical surfaces on both sides, and a ninthlens element L9 formed as a negative lens element concave to the objectside. A diffractive optical surface is arranged on the image side of theninth lens element L9. An aperture diaphragm S is provided between thesecond and third lens units Gr2 and Gr3 so as to move together with thethird lens unit Gr3 during zooming.

FIG. 87 shows the lens construction of the zoom lens system of thetwenty-fourth embodiment, as observed at its wide-angle end (W). Thezoom lens system of the twenty-fourth embodiment is constituted of, fromthe object side, a first lens unit Gr1 having a negative power, a secondlens unit Gr2 having a positive power, a third lens unit Gr3 having apositive power, and a fourth lens unit Gr4 having a negative power anddisposed at the image-side end of the zoom lens system. This zoom lenssystem performs zooming from the wide-angle end [W] to the telephoto end(T) by moving all the lens units toward the object side in such a waythat the distance between the first and second lens units Gr1 and Gr2increases, that the distance between the second and third lens units Gr2and Gr3 increases, and that the distance between the third and fourthlens units Gr3 and Gr4 decreases. In FIG. 87, the arrows m1 to m4schematically indicate the movement of the first to fourth lens unitsGr1 to Gr4 from the wide-angle end (W) to the telephoto end (T).

The first lens unit Gr1 is composed solely of a first lens element L1formed as a negative meniscus lens element concave to the object side.The second lens unit Gr2 is composed solely of a second lens element L2formed as a positive meniscus lens element convex to the object side.The third lens unit Gr3 is composed of, from the object side, a thirdlens element L3 having a negative power and having aspherical surfaceson both sides, and a fourth lens element L4 formed as a positivemeniscus lens element concave to the object side. The fourth lens unitGr4 is composed solely of a fifth lens element L5 formed as a biconcavelens element having aspherical surfaces on both sides and having adiffractive optical surface on the object side. An aperture diaphragm Sis provided between the second and third lens units Gr2 and Gr3 so as tomove together with the third lens unit Gr3 during zooming.

The zoom lens systems of the twenty-second to twenty-fourth embodimentsall have three or more movable lens units that can be movedindependently of one another, and have a negative lens unit at theirimage-side end. In addition, all of these zoom lens systems have adiffractive optical surface arranged within the lens unit disposed attheir image-side end. In a zoom lens system, it is preferable toarrange, as in the twenty-second to twenty-fourth embodiments, adiffractive optical surface within the lens unit disposed at theimage-side end of the zoom lens system where the optical path variesgreatly according to the angle of view, because this makes it possibleto correct properly the lateral chromatic aberration (also calledchromatic aberration of magnification) occurring on the object side.

Tables 26 to 28 below show the construction data of the zoom lenssystems of the twenty-second to twenty-fourth embodiments, respectively.

In the construction data of each embodiment, ri (i=1, 2, 3, . . . )represents the curvature radius of the i-th surface from the objectside, di (i=1, 2, 3, . . . ) represents the i-th axial distance from theobject side, and Ni (i=1, 2, 3, . . . ) and νi (i=1, 2, 3, . . . )respectively represent the d-lines refractive coefficient and the Abbenumber of the i-th lens from the object side. Note that the letter Efound in numerical values listed on the tables indicates that thefigures following it represents an exponent. For example, 1.0E2represents 1.0×102.

Moreover, three values listed for the focal length f and the f-numberFNO of the whole system and for each of those distances between the lensunits which vary with zooming (i.e. the variable axial distances) arethe values at, from left, the wide-angle end [W], the middle focallength [M], and the telephoto end [T].

In the construction data of each embodiment, a surface marked with anasterisk (*) in the curvature radius column is an aspherical surface.The surface shape of an aspherical surface is defined by the followingformula (already noted earlier): $\begin{matrix}{Y = {\frac{C \cdot X^{2}}{1 + \left( {1 - {ɛ \cdot X^{2} \cdot C^{2}}} \right)^{1/2}} + {\sum\limits_{i}{AiX}^{i}}}} & (D)\end{matrix}$

where

X: height in the direction perpendicular to the optical axis;

Y: displacement from the reference surface of the optical axisdirection;

C: paraxial curvature;

ε: quadric surface parameter;

Ai: aspherical coefficient of the i-th order.

Moreover, in the construction data of each embodiment, a surface markedwith [DOE] in the curvature radius column is a surface where adiffractive optical element is provided on the surface of a refractiveoptical element. The phase shape of a diffractive optical element, whichdetermines the pitch of the diffractive optical element, is defined bythe following formula (already noted earlier): $\begin{matrix}{{\varphi (X)} = {2{\pi \cdot {\left( {\sum\limits_{i}{\cdot {Ri} \cdot X^{i}}} \right)/\lambda_{0}}}}} & (E)\end{matrix}$

where

φ(X): phase function;

Ri: phase coefficient of the i-th order;

X: height in the direction perpendicular to the optical axis;

λ0: design wavelength.

Moreover, the twenty-second to twenty-fourth embodiments satisfy thefollowing conditional expressions (1) and (2) (already noted earlier):

0.01<|φdoe/φr|<0.12  (1)

where

φdoe: power of the diffractive optical element;

φr: composite power of the diffractive optical element and therefractive optical surface.

2<|R ₂ ×H _(max)λ₀<|50  (2)

where

R₂: secondary phase coefficient of the diffractive optical element;

H_(max): effective radius of the diffractive optical element;

λ₀: design wavelength.

Table 29 lists the values corresponding to conditional expressions (1)and (2) in the twenty-second to twenty-fourth embodiments.

FIGS. 88A to 88C, 91A to 91C, and 94A to 94C show the aberration at thewide-angle end [W] in the twenty-second to twenty-fourth embodiments,respectively. FIGS. 89A to 89C, 92A to 92C, and 95A to 95C show theaberration at the middle focal length [M] in the twenty-second totwenty-fourth embodiments, respectively. FIGS. 90A to 90C, 93A to 93C,and 96A to 96C show the aberration at the telephoto end [T] in thetwenty-second to twenty-fourth embodiments, respectively. FIGS. 88A to96A illustrate spherical aberration, FIGS. 88B to 96B illustrateastigmatism, and FIGS. 88C to 96C illustrate distortion.

In the spherical aberration diagrams, the solid line (d), broken line(c), and dash-dot line (g) show the aberration for d-lines (wavelength:λd=587.6 nm), c-lines (wavelength: λc=656.3 nm), and g-lines(wavelength: λg=435.8 nm), respectively. In the spherical aberrationdiagrams (horizontal axis: mm), the vertical axis represents h/h0, whichis the height of incidence h normalized by its maximum height h0. In theastigmatism diagrams (horizontal axis: mm) and the distortion diagrams(horizontal axis: %), the vertical axis (MG HT) represents the imageheight (mm). Furthermore, in the astigmatism diagrams, the broken line Mand the solid line S show astigmatism on the meridional surface and onthe sagittal surface, respectively.

TABLE 1 <<Embodiment 1>> f = 31.0˜42.0˜58.0     FNO = 5.37˜7.27˜10.4Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  4.000 r2 ∞ (aperture diaphragm) d2  1.500 r3* −11.393 d3  5.000 N11.51728 ν1 69.43 r4*[DOE]  −6.967 d4 18.996˜13.372˜9.000 r5*  46.296 d5 2.067 N2 1.74400 ν2 44.93 r6*[DOE]  14.738 [Aspherical Coefficient] r3:r4: ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −8.71771E-04 A4 =−0.229803E-04 A6 =  3.52903E-05 A6 = −0.120535E-04 A8 = −1.96982E-05 A8=  0.548957E-06 A10 =  2.81438E-06 A10 = −0.144025E-07 A12 =−1.31353E-07 A14 = −7.51889E-09 A16 =  6.32184E-10 r5: r6: ε =  0.10000× 10 ε =  0.10000 × 10 A4 = −4.46217E-04 A4 = −0.574988E-03 A6 = 2.03439E-06 A6 =  0.607506E-05 A8 =  2.44377E-08 A8 = −0.425041E-07 A10=  3.96291E-10 A10 =  0.122232E-09 A12 = −2.24579E-11 A14 =  2.53395E-13A16 = −8.99427E-16 [Phase Coefficient] r4: r6: R2 = −0.935212E-03 R2 = 0.113616E-02 R4 = −0.529903E-04 R4 =  0.977033E-05 R6 =  0.153323E-04R6 = −0.724598E-06 R8 = −0.286829E-05 R8 =  0.207677E-07 R10 = 0.304137E-06 R10 = −0.294173E-09 R12 = −0.166644E-07 R12 = 0.201337E-11 R14 =  0.363853E-09 R14 = −0.531185E-14

TABLE 2 <<Embodiment 2>> f = 31.0˜36.7˜48.5     FNO = 5.90˜6.99˜9.23Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  2.800 r2 ∞ (aperture diaphragm) d2  1.500 r3* −10.834 d3  4.500 N11.51728 ν1 69.43 r4*[DOE]  −6.979 d4 19.513˜13.912˜6.500 r5*  65.929 d5 3.580 N2 1.74400 ν2 44.93 r6*[DOE]  21.449 [Aspherical Coefficient] r3:r4: ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −7.98322E-04 A4 =−0.130032E-04 A6 = −2.51344E-05 A6 = −0.190665E-04 A8 =  1.45871E-06 A8=  0.857751E-06 A10 = −3.54094E-07 A10 = −0.217195E-07 A12 = −1.76570E-0A14 =  7.97744E-09 A16 = −6.22065E-10 r5: r6: ε =  0.10000 × 10 ε = 0.10000 × 10 A4 = −1.01270E-04 A4 = −0.177819E-03 A6 = −1.66409E-06 A6=  0.882777E-06 A8 =  3.06812E-08 A8 = −0.192044E-08 A10 =  3.37143E-10A10 = −0.154742E-11 A12 = −1.26677E-11 A14 =  1.15143E-13 A16 =−3.52772E-16 [Phase Coefficient] r4: r6: R2 = −0.723770E-03 R2 = 0.318064E-03 R4 = −0.883523E-04 R4 =  0.330954E-04 R6 =  0.254016E-04R6 = −0.160631E-05 R8 = −0.505225E-05 R8 =  0.352324E-07 R10 = 0.603699E-06 R10 = −0.384339E-09 R12 = −0.378775E-07 R12 = 0.203238E-11 R14 =  0.947243E-09 R14 = −0.415012E-14

TABLE 3 <<Embodiment 3>> f = 31.0˜42.0˜58.0     FNO = 5.37˜7.27˜10.04Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  4.200 r2 ∞ (aperture diaphragm) d2  1.500 r3* −9.793 d3  4.786 N11.51728 ν1 69.43 r4*[DOE] −6.435 d4 19.400˜13.777˜9.405 r5* 88.588 d5 2.000 N2 1.74950 ν2 35.27 r6*[DOE] 17.942 [Aspherical Coefficient] r3:r4: ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −9.58060E-04 A4 = 0.202436E-03 A6 =  1.85399E-05 A6 = −0.325545E-04 A8 = −1.66241E-05 A8=  0.148472E-05 A10 =  2.47977E-06 A10 = −0.199811E-07 A12 =−1.20124E-07 A14 = −7.51889E-09 A16 =  6.32184E-10 r5: r6: ε =  0.10000× 10 ε =  0.10000 × 10 A4 = −3.27162E-04 A4 = −0.430316E-03 A6 = 2.73193E-06 A6 =  0.523536E-05 A8 = −1.43226E-08 A8 = −0.405296E-0 A10=  9.13095E-10 A10 =  0.130782E-09 A12 = −2.43145E-11 A14 =  2.38663E-13A16 = −7.99510E-16 [Phase Coefficient] r4: r6: R2 = −0.600000E-03 R2 = 0.130799E-02 R4 = −0.158540E-03 R4 =  0.245930E-04 R6 =  0.283839E-04R6 = −0.127089E-05 R8 = −0.328294E-05 R8 =  0.296381E-07 R10 = 0.256001E-06 R10 = −0.363719E-09 R12 = −0.110943E-07 R12 = 0.225526E-11 R14 =  0.169945E-09 R14 = −0.557561E-14

TABLE 4 <<Embodiment 4>> f = 31.0˜42.0˜60.0     FNO = 5.52˜7.47˜10.67Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  4.200 r2 ∞ (aperture diaphragm) d2  1.500 r3* −8.195 d3  4.378 N11.53172 ν1 48.84 r4*[DOE] −6.138 d4 22.090˜17.436˜13.500 r5* 66.544 d5 1.200 N2 1.74400 ν2 44.93 r6*[DOE] 14.731 [Aspherical Coefficient] r3:r4: ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −1.11056E-03 A4 =−0.123419E-03 A6 =  1.53367E-05 A6 =  0.143980E-04 A8 = −1.68530E-05 A8= −0.195791E-05 A10 =  2.11303E-06 A10 =  0.673502E-07 A12 =−9.25267E-08 A14 = −7.51860E-09 A16 =  6.32422E-10 r5: r6: ε =  0.10000× 10 ε =  0.10000 × 10 A4 = −6.03854E-04 A4 = −0.641492E-03 A6 = 8.81688E-06 A6 =  0.797796E-05 A8 = −1.07481E-07 A8 = −0.539403E-07 A10=  1.98229E-09 A10 =  0.135213E-09 A12 = −2.81430E-11 A14 =  1.93397E-13A16 = −4.89754E-16 [Phase Coefficient] r4: r6: R2 = −0.173581E-02 R2 = 0.220000E-02 R4 = −0.389151E-05 R4 = −0.502200E-04 R6 =  0.309476E-05R6 =  0.135581E-05 R8 = −0.117102E-05 R8 = −0.190929E-07 R10 = 0.150674E-06 R10 =  0.129229E-09 R12 = −0.802067E-08 R12 =−0.340571E-12 R14 =  0.144664E-09 R14 =  0.552881E-16

TABLE 5 <<Embodiment 5>> f = 31.0˜42.0˜52.0     FNO = 5.87˜7.95˜9.18Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  2.800 r2 ∞ (aperture diaphragm) d2  1.500 r3* −10.097 d3  4.505 N11.51680 ν1 64.20 r4*[DOE]  −6.510 d4 19.747˜13.555˜10.200 r5* 214.183 d5 1.200 N2 1.58913 ν2 61.25 r6*  16.610 [Aspherical Coefficient] r3: r4:ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −8.69665E-04 A4 = −0.274223E-04A6 = −4.94222E-05 A6 = −0.286911E-04 A8 =  2.28572E-06 A8 = 0.317969E-05 A10 = −1.85887E-07 A10 = −0.121917E-06 A12 = −3.86667E-08A14 =  8.89596E-09 A16 = −5.22065E-10 r5: r6: ε =  0.10000 × 10 ε = 0.10000 × 10 A4 = −4.36338E-04 A4 = −5.10807E-04 A6 =  3.50451E-06 A6 = 6.19894E-06 A8 =  3.02069E-08 A8 = −4.22271E-08 A10 = −5.60341E-10 A10=  5.38636E-11 A12 = −9.24346E-12 A12 = −2.99200E-13 A14 =  1.97730E-13A14 =  1.26679E-14 A16 = −8.82516E-16 A16 = −5.50742E-17 [PhaseCoefficient] r4: R2 = −0.663605E-03 R4 = −0.428927E-04 R6 = 0.198301E-04 R8 = −0.374353E-05 R10 =  0.327172E-06 R12 = −0.153582E-07R14 =  0.333884E-09

TABLE 6 <<Embodiment 6>> f = 31.0˜42.0˜60.0     FNO = 5.34˜7.24˜10.00Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  4.200 r2 ∞ (aperture diaphragm) d2  1.500 r3*  −8.826 d3  5.000 N11.49140 ν1 57.82 r4*[DOE]  −5.937 d4 18.984˜14.774˜11.500 r5* 3231.825d5  1.200 N2 1.58340 ν2 30.23 r6*[DOE] 14.647 [Aspherical Coefficient]r3: r4: ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −1.11337E-03 A4 =−0.505578E-04 A6 = −2.89599E-06 A6 =  0.161063E-04 A8 = −1.02951E-05 A8= −0.134308E-05 A10 =  1.35800E-06 A10 =  0.383076E-07 A12 =−6.39427E-08 A14 = −7.51889E-09 A16 =  6.32184E-10 r5: r6: ε =  0.10000× 10 ε =  0.10000 × 10 A4 = −5.79337E-04 A4 = −0.676717E-03 A6 = 1.02326E-05 A6 =  0.100777E-04 A8 = −1.45037E-07 A8 = −0.810167E-07 A10=  3.34314E-09 A10 =  0.250979E-09 A12 = −5.91355E-11 A14 =  5.02990E-13A16 = −1.57381E-15 [Phase Coefficient] r4: r6: R2 = −0.139457E-02 R2 = 0.234512E-02 R4 =  0.106953E-04 R4 = −0.129545E-04 R6 = −0.107920E-06R6 =  0.495720E-06 R8 = −0.446277E-06 R8 = −0.124741E-07 R10 = 0.459083E-07 R10 =  0.141972E-09 R12 = −0.132545E-08 R12 =−0.672320E-12 R14 = −0.286015E-11 R14 =  0.880946E-15

TABLE 7 <<Embodiment 7>> f = 31.0˜42.0˜58.0     FNO = 5.58˜7.56˜10.44Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1 ∞d1  4.200 r2 ∞ (aperture diaphragm) d2  1.500 r3*  −9.033 d3  5.000 N11.51728 ν1 69.43 r4*[DOE]  −6.128 d4 19.058˜14.806˜11.500 r5* −120.239d5  1.200 N2 1.58340 ν2 30.23 r6*[DOE]  16.890 [Aspherical Coefficient]r3: r4: ε =  0.10000 × 10 ε =  0.10000 × 10 A4 = −1.07185E-03 A4 = 0.161534E-03 A6 =  6.49986E-06 A6 = −0.303655E-04 A8 = −1.26452E-05 A8=  0.241673E-05 A10 =  1.62801E-06 A10 = −0.704289E-07 A12 =−7.18545E-08 A14 = −7.51889E-09 A16 =  6.32184E-10 r5: r6: ε =  0.10000× 10 ε =  0.10000 × 10 A4 = −5.00028E-04 A4 = −0.614114E-03 A6 = 7.45918E-06 A6 =  0.100553E-04 A8 = −6.30032E-08 A8 = −0.840580E-07 A10=  1.73389E-09 A10 =  0.248961E-09 A12 = −3.52896E-11 A14 =  2.43570E-13A16 = −3.86919E-16 [Phase Coefficient] r4: r6: R2 = −0.918716E-03 R2 = 0.218586E-02 R4 = −0.110740E-03 R4 =  0.175186E-04 R6 =  0.269297E-04R6 = −0.116067E-05 R8 = −0.346183E-05 R8 =  0.293036E-07 R10 = 0.249079E-06 R10 = −0.371407E-09 R12 = −0.105591E-07 R12 = 0.232601E-11 R14 =  0.215386E-09 R14 = −0.574710E-14

TABLE 8 Conditional Conditional Expression (1) Expression (2) Cond.|φdoe/φr| |R₂ × H_(max)/λ₀| Exp.(3) Cond. 1st Lens 2nd Lens 1st Lens 2ndLens |φGr1/ Exp.(4) unit Unit Unit Unit φGr2| ν21 Emb. 1 0.047 0.0685.51 20.69 1.18 — Emb. 2 0.039 0.028 4.07 6.12 1.66 — Emb. 3 0.029 0.0803.53 23.82 1.19 — Emb. 4 0.092 0.113 11.82 43.54 0.97 — Emb. 5 0.033 —3.73 — 1.28 61.25 Emb. 6 0.067 0.118 8.78 42.30 1.02 — Emb. 7 0.0430.111 5.41 39.43 1.03 — N.B.: λ₀ = 585.75 × 10E-6 mm

TABLE 9 << Embodiment 8 >> f=25.8-44.3-73.1 FNO=3.41-5.86-9.67 CurvatureAxial Refractive Radius Distance Coefficient Abbe Number r1* −13.819 d12.800 N1 1.84506 ν1 23.66 r2* −20.233 d2 1.500 r3 237.389 d3 6.440 N21.48749 ν2 70.44 r4 −9.191 d4 1.400 r5 ∞ (aperture diaphragm) d512.077-5.896-2.500 r6*[DOE] −64.240 d6 3.350 N3 1.52510 ν3 56.38 r7*−22.091 d7 3.678 r8 −9.335 d8 1.000 N4 1.78831 ν4 47.32 r9 −65.677[Aspherical Coefficient] r1: r2: ε = −5.400813 ε = −7.887327 A4 =−1.78107E-04 A4 = 1.60475E-04 A6 = 5.50759E-06 A6 = 3.66891E-06 A8 =2.93538E-08 A8 = 1.05499E-07 A10 = −2.40715E-09 A10 = −1.42789E-09 A12 =2.23807E-11 A12 = 3.50091E-11 r6: r7: ε = −734.249329 ε = 0.206632 A4 =−0.111754E-03 A4 = −4.17901E-05 A6 = 0.390159E-05 A6 = −8.29285E-07 A8 =−0.518108E-07 A8 = 2.07422E-08 A10 = 0.507383E-09 A10 = 4.38087E-10 A12= −2.12745E-11 A14 = 1.89823E-13 [Phase Coefficient] r6: R2 =0.153161E-03 R4 = 0.528220E-04 R6 = −0.297302E-05 R8 = 0.572159E-07 R10= −0.394571E-09 R12 = 0.467051E-12

TABLE 10 << Embodiment 9>> f=39.0-75.0-126.1 FNO=3.65-7.03-11.81Curvature Axial Refractive Radius Distance Coefficient Abbe Numberr1*[DOE] 32.688 d1 2.500 N1 1.84506 ν1 23.66 r2* 17.790 d2 3.200 r3−443.624 d3 3.005 N2 1.58267 ν2 46.43 r4 −11.385 d4 1.700 r5 ∞ (aperturediaphragm) d5 15.990-6.407-2.200 r6* −90.552 d6 3.200 N3 1.58340 ν330.23 r7* −29.753 d7 4.205 r8 −11.685 d8 1.000 N4 1.78590 ν4 43.93 r9−59.522 [Aspherical Coefficient] r1: r2: ε = 1.0 ε = 1.0 A4 =−0.321594E-03 A4 = −2.76892E-04 A6 = −0.228864E-05 A6 = −1.57370E-06 A8= 0.692809E-08 A8 = 3.12134E-08 A10 = −0.214450E-090 A10 = 2.37775E-11A12 = −3.80414E-12 r6: r7: ε = 1.0 ε = 1.0 A4 = 5.84118E-05 A4 =−5.11476E-06 A6 = 1.03875E-06 A6 = 1.38172E-06 A8 = −6.21676E-0 A8 =−8.20593E-08 A10 = 1.40589E-09 A10 = 1.73412E-09 A12 = −1.40080E-11 A12= −1.71530E-11 A14 = 5.49874E-14 A14 = 6.65304E-14 [Phase Coefficient]r1: R2 = −0.335464E-03 R4 = 0.384283E-05 R6 = 0.424168E-06 R8 =−0.240853E-07 R10 = 0.632445E-10 R12 = 0.185578E-10 R14 = −0.309215E-12

TABLE 11 << Embodiment 10 >> f=39.1-75.0-112.5 FNO=3.64-6.98-10.48Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1*31.740 d1 2.500 N1 1.58340 ν1 30.23 r2* 15.915 d2 3.497 r3 76.274 d34.000 N2 1.52510 ν2 56.38 r4[DOE] −12.535 d4 1.700 r5 ∞ (aperturediaphragm) d5 14.192-5.471-2.305 r6*[DOE] −60.954 d6 3.200 N3 1.58340 ν330.23 r7* −28.401 d7 4.290 r8 −10.833 d8 1.000 N4 1.78590 ν4 43.93 r9−36.491 [Aspherical Coefficient] r1: r2: ε = 1.0 ε = 1.0 A4 =−3.55029E-04 A4 = −2.87678E-04 A6 = −7.31556E-07 A6 = −6.53773E-07 A8 =−9.04215E-09 A8 = 3.04236E-08 A10 = 2.82648E-11 A10 = 9.95792E-11 A12 =5.26596E-12 A12 = 3.35588E-12 r6: r7: ε = 1.0 ε = 1.0 A4 =0.642592E-04A4 = 9.87099E-06 A6 =0.512484E-06 A6 = 7.51184E-07 A8 = −0.138462E-07 A8= −4.45170E-08 A10 = 0.170728E-09 A10 = 1.07241E-09 A12 = −1 .29625E-11A14 = 6.45127E-14 [Phase Coefficient] r4: r6: R2 = −0.725685E-03 R2 =0.741273E-03 R4 = 0.650060E-05 R4 = −0.180446E-04 R6 = −0.683676E-07 R6= 0.661725E-06 R8 = 0.982012E-09 R8 = −0.189750E-07 R10 = 0.302538E-10R10 = 0.240798E-09 R12 = −0.110810E-11 R12 = −0.108042E-11

TABLE 12 << Embodiment 11 >> f=36.0-46.0-68.0 FNO=5.29-6.77-10.0Curvature Axial Refractive Radius Distance Coefficient Abbe Numberr1*[DOE] 27.576 d1 1.800 N1 1.58913 ν1 61.11 r2 14.970 d2 6.457 r346.570 d3 2.800 N2 1.48794 ν2 70.44 r4 −11.850 d4 1.600 r5 ∞ (aperturediaphragm) d5 11.855-7.857-3.200 r6* −30.608 d6 2.500 N3 1.58340 ν330.23 r7 14.439 d7 2.666 r8 −8.978 d8 1.000 N4 1.66755 ν4 41.98 r9−54.603 [Aspherical Coefficient] r1: r6: ε = 14.478606 ε = 5.947800 A4 =−0.187833-03 A4 = 9.86210E-05 A6 = −0.230469-05 A6 = −5.45510E-07 A8 =−0.254578-07 A8 = 4.95370E-08 A10 = −0.139817-09 A10 = −6.87010E-10 A12= 4.97500E-12 [Phase Coefficient] r1: R2 = −0.900000E-03 R4 =0.200481E-04 R6 = −0.477910E-06 R8 = 0.220685E-08 R10 = −0.251251E-09R12 = 0.600675E-11

TABLE 13 << Embodiment 12 >> f=39.0-75.00-126.1 FNO=3.64-7.00-11.77Curvature Axial Refractive Radius Distance Coefficient Abbe Number r1*33.614 d1 2.348 N1 1.84506 ν1 23.66 r2* 24.735 d2 3.894 r3 −64.015 d33.300 N2 1.58144 ν2 40.83 r4[DOE] −12.660 d4 1.700 r5 ∞ (aperturediaphragm) d5 16.257-6.488-2.200 r6* −384.511 d6 3.200 N3 1.58340 ν330.23 r7* −27.851 d7 3.550 r8 −11.978 d8 1.000 N4 1.80518 ν4 25.43r9[DOE] −75.583 [Aspherical Coefficient] r1: r2: ε = 1.0 ε = 1.0 A4 =−2.21481E-04 A4 = −1.64351E-04 A6 = −1.82011E-06 A6 = −2.15286E-06 A8 =−2.30964E-09 A8 = 1.38950E-08 A10 = −5.55286E-10 A10 = −1.13309E-10 A12= 1.37000E-11 A12 = 7.87022E-12 r6: r7: ε = 1.0 ε = 1.0 A4 = 4.88983E-05A4 = −6.39356E-06 A6 = 2.21301E-06 A6 = 2.37182E-06 A8 = −1.00499E-07 A8= −1.05632E-07 A10 = 1.85369E-09 A10 = 1.73575E-09 A12 = −1.53753E-11A12 = −1.38838E-11 A14 = 5.30171E-14 A14 = 4.96907E-14 [PhaseCoefficient] r4: r9: R2 = −0.120000E-02 R2 = 0.267414E-02 R4 =0.267114E-05 R4 = −0.151264E-04 R6 = 0.572067E-07 R6 = 0.195100E-06 R8 =0.650686E-09 R8 = −0.186834E-08 R10 = 0.339992E-10 R10 = 0.768360E-11R12 = −0.175055E-11 R12 = −0.618651E-14

TABLE 14 Conditional Conditional Expression (5) Expression (6) |φdoe /φr| |R₂ × H_(max) / λ₀| 1st Lens 2nd Lens 1st Lens 2nd Lens Unit UnitUnit Unit Emb. 8 — −0.006  —  2.20 Emb. 9 0.021 — 3.10 — Emb. 10 0.0410.038 7.56 11.73 Emb. 11 0.044 — 8.42 — Emb. 12 0.073 0.140 12.32  56.16N.B.: λ₀ = 585.75 × 10E-6 mm

TABLE 15 << Embodiment 13 >> f=36.0-46.0-68.0 FNO=5.85-7.47-11.04Curvature Axial Refractive Radius Distance Coefficient Abbe Number<First Lens Unit, positive> r1* 16.654 d1 1.700 N1 1.58340 ν1 30.23r2*[DOE] 11.158 d2 6.800 r3 27.642 *d3 4.500 N2 1.48749 ν2 70.44 r4−15.451 d4 1.530 r5 ∞ (aperture diaphragm A) d5 20.246-15.972-11.000<Second Lens Unit, negative> r6* 11.119 d6 1.000 N3 1.49300 ν3 58.34 r7*-80.645 [Aspherical Coefficient] r1: r2: ε = 1.0000 ε = 1.0000 A4 =−5.07167E-04 A4 = −0.537417E-03 A6 = 5.94882E-06 A6 = 0.637132E-05 A8 =−1.77015E-07 A8 = −0.231016E-06 A10 = 1.47358E-09 A10 = 0.340251E-08 A12= 2.42637E-11 A14 = −3.34003E-13 r6: r7: ε = 1.0000 ε = 1.0000 A4 =3.57900E-04 A4 = 1.88550E-4 A6 = −1.46737E-05 A6 = −3.71495E-6 A8 =4.93788E-07 A8 = 3.53529E-8 A10 = −1.07105E-08 A10 = −1.95050E-10 A12 =1.18188E-10 A12 = 6.55611E-13 A14 = −4.95732E-13 A14 = −1.15257E-15[Phase Coefficient] r2: R2 = −0.275811E-3 R4 = −0.338384E-6 R6 =0.364960E-6 R8 = −0.119618E-7

TABLE 16 << Embodiment 14 >> f=36.0-46.0-67.9 FNO=5.58-7.13-10.54Curvature Axial Refractive Radius Distance Coefficient Abbe Number<First Lens Unit, positive> r1* 23.745 d1 1.900 N1 1.58340 ν1 30.23r2*[DOE] 13.793 d2 2.770 r3 −132.219 d3 4.500 N2 1.48749 ν2 70.44 r4−9.350 d4 1.530 r5 ∞ (aperture diaphragm A) d5 21.400-16.596-11.000<Second Lens Unit, negative> r6*[DOE] −12.282 d6 1.000 N3 1.49300 ν358.34 r7* −80.645 [Aspherical Coefficient] r1: r2: ε = 1.0000 ε = 1.0000A4 = −5.38458E-4 A4 = −0.413958E-3 A6 = 3.83305E-6 A6 = 0.669438E-5 A8 =−3.10785E-7 A8 = 0.323274E-6 A10 = 4.02904E-9 A10 = 0.838167E-8 A12 =1.71740E-10 A14 = −4.60595E-12 r6: r7: ε = 1.0000 ε = 1.0000 A4 =0.265508E-3 A4 = 1.51743E-4 A6 = −0.506093E-5 A6 = −3.03061E-6 A8 =0.702829E-7 A8 = 3.64965E-8 A10 = −0.276735E-9 A10 = −2.14382E-10 A12 =6.20757E-13 A14 = −7.75422E-16 [Phase Coefficient] r2: r6: R2 =−0.268363E-3 R2 = 0.376259E-3 R4 = 0.137123E-4 R4 = 0.188764E-5 R6 =0.282505E-6 R6 = 0.710741E-7 R8 = 0.259606E-8 R8 = 0.506955E-9

TABLE 17 << Embodiment 15 >> f = 36.0˜46.0˜68.0 FNO = 5.69˜7.27˜10.74Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* 149.320 d1 2.249 N1 1.58340 v1 30.23 r2*25.291 d2 1.039 r3 −60.177 d3 4.500 N2 1.48749 v2 70.44 r4 −8.508 d41.530 r5 ∞ (aperture diaphragm A) d5 22.486˜17.1296˜10.889 <Second LensUnit, negative> r6*[DOE] −13.278 d6 1.000 N3 1.49300 v3 58.34 r7*−80.645 [Aspherical Coefficient] r1: r2: ε = 1.0000 ε = 1.0000 A4 =−6.55457E−4 A4 = −3.77904E−4 A6 = 1.11500E−5 A6 = 1.33495E−5 A8 =−9.86513E−7 A8 = −8.22387E−7 A10 = 2.90576E−8 A10 = 2.43242E−8 A12 =−1.32184E−10 A14 = −6.50647E−12 r6: r7: ε = 1.0000 ε = 1.0000 A4 =0.274942E−3 A4 = 1.66120E−4 A6 = −0.531916E−5 A6 = −3.27185E−6 A8 =0.628429E−7 A8 = 3.65853E−8 A10 = −0.221283E−9 A10 = −2.15009E−10 A12 =6.99825E−13 A14 = −1.07237E-15 [Phase Coefficient] r6: R2 = 0.406319E−3R4 = 0.222987E−5 R6 = −0.598544E−7 R8 = 0.345163E−9

TABLE 18 << Embodiment 16 >> f = 36.0˜46.0˜68.0 FNO = 5.81˜7.42˜10.97Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* −51.746 d1 2.324 N1 1.58340 v1 30.23 r2*25.200 d2 1.000 r3 198.839 d3 3.000 N2 1.52510 v2 56.38 r4 −8.701 d41.530 r5 ∞ (aperture diaphragm A) d5 23.273˜17.604˜11.000 <Second LensUnit, negative> r6*[DOE] −16.522 d6 1.000 N3 1.58340 v3 30.23 r7*−80.645 [Aspherical Coefficient] r1: r2: ε = 1.0000* ε = 1.0000 A4 =−9.05597E−4 A4 = −5.86654E−4 A6 = 1.65762E−5 A6 = 1.79045E−5 A8 =−1.37845E−6 A8 = −8.09925E−7 A10 = 5.20321E−8 A10 = 2.20014E−8 A12 =−5.01423E−10 A14 = −1.20666E−11 r6: r7: ε = 1.0000 ε = 1.0000 A4 =0.189916E−3 A4 = 1.23891E−4 A6 = −0.546697E−5 A6 = −3.42025E−6 A8 =0.632287E−7 A8 = 4.11279E−8 A10 = −0.230735E−9 A10 = −2.38886E−10 A12 =6.91989E−13 A14 = −8.69625E−16 [Phase Coefficient] r6: R2 = 0.116752E−2R4 = 0.274912E−5 R6 = −0.595954E−7 R8 = 0.348817E−9

TABLE 19 << Embodiment 17 >> f = 36.0˜46.0˜68.0 FNO = 5.75˜7.35˜10.87Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* −103.503 d1 2.365 N1 1.58340 v1 30.23r2* 23.510 d2 1.000 r3 240.314 d3 3.433 N2 1.49300 v2 58.34 r4 −8.507 d41.530 r5 ∞ (aperture diaphragm A) d5 22.777˜17.336˜11.000 <Second LensUnit, negative> r6*[DOE] −13.350 d6 1.000 N3 1.49300 v3 58.34 r7*−80.645 [Aspherical Coefficient] r1: r2: ε = 1.0000 ε = 1.0000 A4 =−8.52518E−4 A4 = −5.54868E−4 A6 = 1.79885E−5 A6 = 2.00155E−5 A8 =−1.55255E−6 A8 = −1.07505E−6 A10 = 6.28122E−8 A10 = 3.06323E−8 A12 =−1.03840E−9 A14 = 6.76065E−14 r6: r7: ε = 1.0000 ε = 1.0000 A4 =0.274483E−3 A4 = 1.76926E−4 A6 = −0.600937E−5 A6 = −3.73239E−6 A8 =0.712624E−7 A8 = 4.18494E−8 A10 = −0.263854E−9 A10 = −2.35231E−10 A12 =6.52573E−13 A14 = −7.50393E−16 [Phase Coefficient] r6: R2 = 0.306284E−3R4 = 0.296471E−6 R6 = −0.241019E−7 R8 = 0.216855E−9

TABLE 20 << Embodiment 18 >> f = 36.0˜46.0˜73.0 FNO = 5.38˜6.87˜10.91Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* −136.152 d1 1.700 N1 1.58340 v1 30.23r2* 43.255 d2 4.000 r3 −71.569 d3 3.000 N2 1.49300 v2 58.34 r4[DOE]−9.196 d4 1.530 r5 ∞ (aperture diaphragm A) d5 23.007˜18.021˜11.000<Second Lens Unit> r6* −12.366 d6 1.000 N3 1.49300 v3 58.34 r7* −80.645[Aspherical Coefficient] r1: r2: ε = 1.0000 ε = 1.0000 A4 = −4.14596E−4A4 = −1.43587E−4 A6 = 1.87797E−5 A6 = 1.34918E−5 A8 = −1.70605E−6 A8 =−6.17394E−7 A10 = 9.26432E−8 A10 = 1.68564E−8 A12 = −2.66885E−9 A14 =3.10523E−11 r6: r7: ε = 1.0000 ε = 1.0000 A4 = 4.58029E−4 A4 =3.17412E−4 A6 = −6.24285E−6 A6 = −4.79974E−6 A8 = 5.18647E−8 A8 =4.08806E−8 A10 = −1.28833E−10 A10 = −1.96731E−10 A12 = 5.44119E−13 A14 =−7.18496E−16 [Phase Coefficient] r4: R2 = −0.400000E−3 R4 = −0.690307E−6R6 = 0.100244E−5 R8 = −0.357162E−7

TABLE 21 Conditional Conditional Expression (7) Expression (8) Cond. 1stLens 2nd Lens 1st Lens 2nd Lens Cond. Exp. unit Unit Unit Unit Exp. (9)(10) Emb. 13 0.015 — 1.60 — 0.015 — Emb. 14 0.015 0.022 1.92 6.40 0.0150.022 Emb. 15 — 0.026 — 6.91 — 0.026 Emb. 16 — 0.077 — 21.47  — 0.077Emb. 17 — 0.020 — 5.63 — 0.020 Emb. 18 0.022 — 2.66 — 0.022 —

TABLE 22 << Embodiment 19 >> f = 36.0˜46.0˜68.0 FNO = 6.04˜7.72˜11.42Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* −15.777 d1 5.736 N1 1.51178 v1 69.07r2*[DOE] −8.974 d2 2.000 r3 ∞ (aperture diaphragm A) d317.633˜10.412˜2.000 <Second Lens Unit, negative> r4* −63.020 d4 3.500 N21.58340 v2 30.23 r5* −16.846 d5 2.500 r6 −13.072 d6 1.000 N3 1.70154 v341.15 r7 −1836.058 [Aspherical Coefficient] r1: r2: ε = 1.0000 ε =1.0000 A4 = −5.06810E−04 A4 = −0.156896E−3 A6 = 7.89450E−06 A6 =0.852515E−5 A8 = −1.51723E−06 A8 = −0.425178E−6 A10 = 1.16596E−07 A10 =0.109571E−7 A12 =−7.06037E−10 A14 = −2.20494E−10 r4: r5: ε = 1.0000 ε =1.0000 A4 = −6.93937E−05 A4 = −7.49983E−5 A6 = 5.45272E−06 A6 =1.35208E−6 A8 = −2.19136E−07 A8 = 2.07437E−8 A10 = 2.58014E−09 A10 =−2.59620E−9 A12 = 4.45085E−12 A12 = 4.41162E−11 A14 = −2.14069E−13 A14 =−2.18639E−13 A16 = 7.47946E−16 [Phase Coefficient] r2: R2 = −0.929904E−3 R4 = 0.944877E−5 R6 = −0.177246E−6 R8 = −0.104687E−7

TABLE 23 << Embodiment 20 >> f = 36.0˜46.0˜68.0 FNO = 6.04˜7.72˜11.40Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* −15.601 d1 5.603 N1 1.52510 v1 56.38r2*[DOE] −8.929 d2 2.000 r3 ∞ (aperture diaphragm A) d316.335˜9.712˜2.000 <Second Lens Unit, negative> r4* −43.567 d4 3.500 N21.58340 v2 30.23 r5* −15.754 d5 2.563 r6 −12.487 d6 1.000 N3 1.70154 v341.15 r7 −200.13 [Aspherical Coefficient] r1: r2: ε = 1.0000 ε = 1.0000A4 = −5.27500E−04 A4 = −0.135035E−3 A6 = 6.19560E−06 A6 = 0.502407E−5 A8= −7.74378E−07 A8 = −0.250180E−6 A10 = 2.92740E−08 A10 = 0.835102E−8 A12= 2.36962E−09 A14 = −2.20494E−10 r4: r5: ε = 1.0000 ε = 1.0000 A4 =−6.06687E−5 A4 = −8.04087E−5 A6 = 5.75569E−6 A6 = 2.22370E−6 A8 =−3.30651E−7 A8 = −1.82096E−8 A10 = 5.73424E−9 A10 = −2.71279E−9 A12 =−2.61719E−11 A12 = 5.83952E−11 A14 = −1.08150E−13 A14 = −3.29099E−13 A16= 5.13656E−16 [Phase Coefficient] r2: R2 = −0.111435E−2 R4 = 0.356259E−5R6 = 0.625222E−6 R8 = −0.467672E−7

TABLE 24 << Embodiment 21 >> f = 36.0˜46.0˜68.0 FNO = 6.15˜7.85˜11.61Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1* −18.803 d1 5.725 N1 1.49300 v1 58.34r2*[DOE] −9.113 d2 2.000 r3 ∞ (aperture diaphragm A) d314.208˜8.568˜2.000 <Second Lens Unit, negative> r4* −30.000 d4 3.152 N21.58340 v2 30.23 r5*[DOE] −15.877 d5 3.500 r6 −10.551 d6 1.000 N31.58340 v3 30.23 r7 −59.237 [Aspherical Coefficient] r1: r2: ε = 1.0000ε = 1.0000 A4 = −5.95580E−4 A4 = −0.218116E−3 A6 = 4.06040E−5 A6 =0.165267E−4 A8 = −1.25117E−5 A8 = −0.104547E−5 A10 = 1.92444E−6 A10 =0.261682E−7 A12 = −1.4OS97E−7 A14 = 3.85081E−9 r4: r5: ε = 1.0000 ε =1.0000 A4 = 9.41188E−6 A4 = 0.147440E−4 A6 = 4.18634E−6 A6 = 0.735909E−7A8 = −1.04362E−7 A8 = 0.265375E−7 A10 = 2.42448E−9 A10 = −0.153544E−9A12 = −3.08900E−11 A14 = 1.94111E−13 A16 = −4.70429E−16 [PhaseCoefficient] r2: R2 = 0.154115E−2 R4 = 0.322548E−5 R6 = −0.640151E−6 R8= 0.296073E−7 r5: R2 = 0.166105E−2 R4 = 0.814228E−5 R6 = −0.147822E−7 R8= 0.874974E−9

TABLE 25 Conditional Conditional Expression (12) Expression (13) 1st 2nd1st 2nd Lens Lens Lens Lens Cond. Exp. Cond. Exp. unit Unit Unit Unit(14) (15) Emb. 19 0.055 — 5.94 — 0.055 — Emb. 20 0.064 — 7.11 — 0.064 —Emb. 21 0.084 0.113 8.66 24.26 0.084 0.113

TABLE 26 << Embodiment 22 >> f = 22.7˜42.6˜85 FNO = 6.0˜8.3˜11.1Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1 −38.000 d1 1.000 N1 1.84666 v1 23.83 r2−75.979 d2 0.100 r3 9.264 d3 2.204 N2 1.48749 v2 70.44 r4 20.476 d42.957˜6.902˜9.446 <Second Lens Unit, positive> r5 ∞ (Aperture DiaphragmS) d5 1.300 r6* ∞ d6 1.050 N3 1.52200 v3 52.20 r7* 18.233 d7 1.300 r8−29.211 d8 2.200 N4 1.67790 v4 55.52 r9 −6.466 d9 8.089˜4.144˜1.600<Third Lens Unit, negative> r10*[DOE] −13.722 d10 0.950 N5 1.76743 v549.48 r11* 42.000 [Aspherical Coefficient] r6: r7: ε = 0.10000E+ 01 ε =0.10000E+01 A4 = −0.23870E−02 A4 = −0.10194E−02 A6 = 0.17248E−03 A6 =−0.16281E−03 A8 = 0.27765E−04 A8 = 0.30729E−04 A10 = −0.31158E−05 A10 =−0.29920E−05 A12 = 0.13411E−06 A12 = 0.12008E−06 r10: r11: ε = −13.7218ε = 0.10000E+01 A4 = −0.87668E−03 A4 = −0.20715E−03 A6 = 0.22263E−04 A6= −0.69046E−06 A8 = −0.33997E−06 A8 = 0.22862E−06 A10 = 0.22078E−08 A10= −0.77305E−08 A12 = 0.12575E−09 A14 = −0.10343E−11 A16 = 0.34528E−14[Phase Coefficient] r10: R2 = 0.546733E−03 R4 = −0.500338E−04 R6 =0.137714E−05

TABLE 27 << Embodiment 23 >> f = 22.5˜70˜126 FNO = 5.6˜7.1˜10.1Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, positive> r1 15.703 d1 1.000 N1 1.84666 v1 23.82 r213.043 d2 0.100 r3 13.043 d3 2.800 N2 1.48749 v2 70.44 r4 49.391 d41.200˜10.985˜15.000 <Second Lens Unit, negative> r5* −82.538 d5 0.700 N31.77250 v3 49.77 r6 9.877 d6 1.300 r7 11.569 d7 1.500 N4 1.84666 v423.82 r8 20.376 d8 7.531˜2.873˜0.650 <Third Lens Unit, positive> r9 ∞(Aperture Diaphragm S) d9 0.100 r10 8.271 d10 3.200 N5 1.48749 v5 70.44r11 −57.085 d11 0.100 r12* 22.188 d12 1.200 N6 1.84666 v6 23.82 r1311.951 d13 0.700 r14 −406504.062 d14 2.500 N7 1.48749 v7 70.44 r15−9.546 d15 7.419˜2.292˜0.500 <Fourth Lens Unit, negative> r16* −14.507d16 2.400 N8 1.62017 v8 24.01 r17* −9.240 d17 0.950 r18 −7.979 d18 0.800N9 1.75450 v9 51.57 r19[DOE] ∞ [Aspherical Coefficient] r5: r12: ε =0.10000E+01 ε = 0.10000E+01 A4 = −0.10142E−04 A4 = −0.31379E−03 A6 =−0.26311E−07 A6 = 0.10567E−05 A8 = −0.23454E−07 A8 = −0.39053E−06 A10 =0.90300E−09 A10 = 0.14936E−07 A12 = −0.11120E−10 A12 = −0.24728E−09 r16:r17: ε = 0.10000E+01 ε = 0.10000E+01 A4 = 0.82022E−04 A4 = 0.68833E−04A6 = −0.10607E−05 A6 = 0.25075E−05 A8 = 0.17515E−06 A8 = −0.57735E−07A10 = −0.24991E−08 A10 = 0.28228E−08 A12 = −0.19148E−11 A12 =−0.51055E−10 [Phase Coefficient] r19: R2 = 0.258403E−03 R4 =0.754573E−05 R6 = −0.349205E−06 R8 = 0.135350E−08 R10 = 0.645101E−10 R12= −0.583544E−12

TABLE 28 << Embodiment 24 >> f = 22.9˜42.9˜85.0 FNO = 6.0˜8.4˜11.6Curvature Axial Refractive Abbe Radius Distance Coefficient Number<First Lens Unit, negative> r1 −47.069 d1 1.000 N1 1.84666 v1 23.83 r2−107.390 d2 0.100˜1.086˜2.500 <Second Lens Unit, positive> r3 9.266 d32.085 N2 1.48749 v2 70.44 r4 19.222 d4 2.836˜6.782˜9.322 <Third LensUnit, positive> r5 ∞ (Aperture Diaphragm S) d5 1.300 r6* −1010.611 d61.050 N3 1.52200 v3 52.20 r7* 19.972 d7 1.500 r8 −33.534 d8 2.243 N41.67790 v4 55.52 r9 −6.728 d9 8.086˜4.140˜1.600 <Fourth Lens Unit,negative> r10*[DOE] −13.557 d10 0.950 N5 1.76743 v5 49.48 r11* 42.000[Aspherical Coefficient] r6: r7: ε = 0.10000E+01 ε = 0.10000E+01 A4 =−0.19994E−02 A4 = −0.86073E−03 A6 = −0.16995E−03 A6 = −0.13114E−03 A8 =0.28941E−04 A8 = 0.25614E−04 A10 = −0.31516E−05 A10 = −0.25964E−05 A12 =0.13031E−06 A12 = 0.10592E-06 r10: r11: ε = −13.5569 ε = 0.10000E+01 A4= −0.59404E−03 A4 = −0.20972E−03 A6 = 0.62519E−05 A6 = −0.30902E−05 A8 =0.71458E−08 A8 = 0.28885E−06 A10 = −0.47607E−09 A10 = −0.81181E−08 A12 =0.12180E−09 A14 = −0.96635E−12 A16 = 0.31711E−14 [Phase Coefficient]r10: R2 = 0.365392E−03 R4 = −0.479462E−04 R6 = 0.216423E−05 R8 =0.575454E−07 R10 = 0.926640E−09 R12 = 0.662751E−11

TABLE 29 Conditional Conditional Expression (1) Expression (2) |φdoe/φr|R₂ × H_(max)/λ₀ Emb. 22 0.0144 6.51 Emb. 23 0.0074 3.99 Emb. 24 0.00954.35

What is claimed is:
 1. A zoom lens system that has a plurality of lensunits including a lens unit having a negative power disposed at animage-side end and that performs zooming by varying distances between aplurality of lens units, wherein one of said plurality of lens unitsincludes a surface having a power to diffract light and, wherein thefollowing conditional expression is satisfied: 0.01<|φdoe/φr|<0.12where: φdoe: diffractive power of the surface having a power to diffractlight; and φr: composite power of the diffractive and refractive powersof the lens unit that includes the surface having a power to diffractlight.
 2. A zoom lens system as claimed in claim 1, wherein the zoomlens system has at least four lens units.
 3. A zoom lens system asclaimed in claim 1, wherein the zoom lens system comprises, from theobject side: a first lens unit having a positive power; a second lensunit having a positive power; and a third lens unit having a negativepower.
 4. A zoom lens system as claimed in claim 1, wherein the zoomlens system comprises, from the object side: a first lens unit having apositive power; a second lens unit having a negative power, a third lensunit having a positive power; and a fourth lens unit having a negativepower.
 5. A zoom lens system as claimed in claim 1, wherein the zoomlens system comprises, from the object side: a first lens unit having anegative power; a second lens unit having a positive power; a third lensunit having a positive power; and a fourth lens unit having a negativepower.
 6. A zoom lens system as claimed in claim 1, wherein the surfacehaving a power to diffract light is made from plastic material.
 7. Azoom lens system as claimed in claim 1, wherein the surface having apower to diffract light is formed on a glass lens element.
 8. A zoomlens system as claimed in claim 1, wherein the surface having a power todiffract light is made from plastic material by injection-moldingtogether with a lens element.
 9. A zoom lens system as claimed in claim1, wherein the lens unit having a negative power disposed at theimage-side end is composed of one lens element.
 10. A zoom lens systemas claimed in claim 1, wherein the lens unit having a negative powerdisposed at the image-side end is composed of, from the object side, apositive lens element and a negative lens element.
 11. A zoom lenssystem that has a plurality of lens units including a lens unit having anegative power disposed at an image-side end and that performs zoomingby varying distances between a plurality of lens units, wherein one ofsaid plurality of lens units includes a surface having a power todiffract light and, wherein the following conditional expression issatisfied: 2<|R ₂ ×H _(max)/λ₀|<50 where R₂: secondary phase coefficientof the surface having a power to diffract light; H_(max): effectiveradius of the surface having a power to diffract light; and λ₀: designwavelength.
 12. A zoom lens system as claimed in claim 11, wherein thezoom lens system has at least four lens units.
 13. A zoom lens system asclaimed in claim 11, wherein the zoom lens system comprises, from theobject side: a first lens unit having a positive power, a second lensunit having a positive power; and a third lens unit having a negativepower.
 14. A zoom lens system as claimed in 11, wherein the zoom lenssystem comprises, from the object side: a first lens unit having apositive power; a second lens unit having a negative power; a third lensunit having a positive power; and a fourth lens unit having a negativepower.
 15. A zoom lens system as claimed in claim 11, wherein the zoomlens system comprises, from the object side: a first lens unit having anegative power; a second lens unit having a positive power; a third lensunit having a positive power; and a fourth lens unit having a negativepower.
 16. A zoom lens system as claimed in claim 11, wherein thesurface having a power to diffract light is made from plastic material.17. A zoom lens system as claimed in claim 11, wherein the surfacehaving a power to diffract light is formed on a glass lens element. 18.A zoom lens system as claimed in claim 11, wherein the surface having apower to diffract light is made from plastic material byinjection-molding together with a lens element.
 19. A zoom lens systemas claimed in claim 11, wherein the lens unit having a negative powerdisposed at the image-side end is composed of one lens element.
 20. Azoom lens system as claimed in claim 11, wherein the lens unit having anegative power disposed at the image-side end is co posed of, from theobject side, a positive lens element and a negative lens element.
 21. Azoom lens system for use as a taking optical system of a camera,comprising: at least one lens unit having a positive power; and a lensunit having a negative power disposed at an image-side end, wherein thezoom lens system performs zooming by varying distances between lensunits, wherein one of the lens units includes a surface having a powerto diffract light, wherein the following conditional expression issatisfied: 0.01<|φdoe/φr|<0.12 where: φdoe: diffractive power of thesurface having a power to diffract light; and φr: composite power of thediffractive and refractive powers of the lens unit that includes thesurface having a power to diffract light.
 22. A zoom lens system asclaimed in claim 21, wherein the surface having a power to diffractlight is made from plastic material by injection-molding together with alens element.
 23. A zoom lens system as claimed in claim 21, wherein thelens unit having a negative power disposed at the image-side end iscomposed of one lens element.
 24. A zoom lens system as claimed in claim21, wherein the lens unit having a negative power disposed at theimage-side end is composed of, from the object side, a positive lenselement and a negative lens element.
 25. A zoom lens system as claimedin claim 21, wherein the zoom lens system has a least four lens units.26. A zoom lens system as claimed in claim 21, wherein the zoom lenssystem comprises, from the object side: a first lens unit having apositive power; a second lens unit having a positive power; and a thirdlens unit having a negative power, said third lens unit including thesurface having a power to diffract light.
 27. A zoom lens system asclaimed in claim 21, wherein the zoom lens system comprises, from theobject side: a first lens unit having a positive power; a second lensunit having a negative power; a third lens unit having a positive power;and a fourth lens unit having a negative power.
 28. A zoom lens systemas claimed in claim 21, wherein the zoom lens system comprises, from theobject side: a first lens unit having a negative power; a second lensunit having a positive power; a third lens unit having a positive power;and a fourth lens unit having a negative power.
 29. A zoom lens systemas claimed in claim 21, wherein the surface having a power to diffractlight is made from plastic material.
 30. A zoom lens system as claimedin claim 21, wherein the surface having a power to diffract light isformed on a glass lens element.
 31. A zoom lens system for use as anoptical system of a camera, comprising: at least one lens unit having apositive power; and a lens unit having a negative power disposed at animage-side end, wherein the zoom lens system performs zooming by varyingdistances between lens units, and, wherein one of the lens unitsincludes a surface having a power to diffract light, wherein thefollowing conditional expression is satisfied: 2<|R ₂ ×H _(max)/λ₀|<50where R₂: secondary phase coefficient of the surface having a power todiffract light; H_(max): effective radius of the surface having a powerto diffract light; and λ₀: design wavelength.
 32. A zoom lens system asclaimed in claim 31, wherein the zoom lens system has at least four lensunits.
 33. A zoom lens system as claimed in claim 31, wherein the zoomlens system comprises, from the object side: a first lens unit having apositive power; a second lens unit having a positive power; and a thirdlens unit having a negative power, said third lens unit including thesurface having a power to diffract light.
 34. A zoom lens system asclaimed in claim 31, wherein the zoom lens system comprises, from theobject side: a first lens unit having a positive power; a second lensunit having a negative power; a third lens unit having a positive power;and a fourth lens unit having a negative power.
 35. A zoom lens systemas claimed in claim 31, wherein the zoom lens system comprises, from theobject side: a first lens unit having a negative power; a second lensunit having a positive power; a third lens unit having a positive power;and a fourth lens unit having a negative power.
 36. A zoom lens systemas claimed in claim 31, wherein the surface having a power to diffractlight is made from plastic material.
 37. A zoom lens system as claimedin claim 31, wherein the surface having a power to diffract light isformed on a glass lens element.
 38. A zoom lens system as claimed inclaim 31, wherein the surface having a power to diffract light is madefrom plastic material by injection-molding together with a lens element.39. A zoom lens system as claimed in claim 31, wherein the lens unithaving a negative power disposed at the image-side end is composed ofone lens element.
 40. A zoom lens system as claimed in claim 31, whereinthe lens unit having a negative power disposed at the image-side end iscomposed of, from the object side, a positive lens element and anegative lens element.
 41. A zoom lens system comprising: a plurality oflens units; and a lens unit having a negative power and provided at theimage-side end of the zoom lens system, the lens unit consisting of asingle lens element having a surface having a power to diffract light,wherein the zoom lens system performs zooming by varying distancesbetween lens units including said lens-unit.
 42. A zoom lens systemcomprising: a lens unit having a negative power and provided at theimage-side end of the zoom lens system, the lens unit consisting of afirst single lens element having a positive power and a second singlelens element having a negative power, the lens unit having a surfacehaving a power to diffract light, wherein the zoom lens system performszooming by varying distances between lens units including said lensunit.
 43. A zoom lens system as claimed in claim 42, wherein the surfaceis provided on the second single lens element.